diff --git a/src/main/java/com/zipcodewilmington/danny_do_better_exercises/MathUtilities.java b/src/main/java/com/zipcodewilmington/danny_do_better_exercises/MathUtilities.java
index 8076dfe..8d97110 100644
--- a/src/main/java/com/zipcodewilmington/danny_do_better_exercises/MathUtilities.java
+++ b/src/main/java/com/zipcodewilmington/danny_do_better_exercises/MathUtilities.java
@@ -1,5 +1,7 @@
 package com.zipcodewilmington.danny_do_better_exercises;
 
+import java.nio.ByteBuffer;
+
 /**
  * Created by dan on 6/14/17.
  */
@@ -11,7 +13,8 @@ public class MathUtilities {
      * @return sum of `baseValue` and `difference`
      */
     public Integer add(int baseValue, int difference) {
-        return null;
+
+        return baseValue + difference;
     }
 
     /**
@@ -20,7 +23,7 @@ public Integer add(int baseValue, int difference) {
      * @return sum of `baseValue` and `difference`
      */
     public Long add(long baseValue, long difference) {
-        return null;
+        return baseValue + difference;
     }
 
     /**
@@ -28,8 +31,12 @@ public Long add(long baseValue, long difference) {
      * @param difference value to add to starting value
      * @return sum of `baseValue` and `difference`
      */
-    public Short add(short baseValue, short difference) {
-        return null;
+    public int add(short baseValue, short difference) {
+
+        int i = baseValue;
+        int j = difference;
+        return i + j;
+
     }
 
     /**
@@ -38,7 +45,11 @@ public Short add(short baseValue, short difference) {
      * @return sum of `baseValue` and `difference`
      */
     public Byte add(byte baseValue, byte difference) {
-        return null;
+
+        return (byte)(baseValue + difference);
+
+
+
     }
 
     /**
@@ -47,7 +58,7 @@ public Byte add(byte baseValue, byte difference) {
      * @return sum of `baseValue` and `difference`
      */
     public Float add(float baseValue, float difference) {
-        return null;
+        return baseValue + difference;
     }
 
     /**
@@ -56,7 +67,8 @@ public Float add(float baseValue, float difference) {
      * @return sum of `baseValue` and `difference`
      */
     public Double add(double baseValue, double difference) {
-        return null;
+        return baseValue + difference;
+
     }
 
     /**
@@ -65,7 +77,8 @@ public Double add(double baseValue, double difference) {
      * @return difference between `baseValue` and `difference`
      */
     public Integer subtract(int baseValue, int difference) {
-        return null;
+
+        return baseValue - difference;
     }
 
     /**
@@ -74,7 +87,7 @@ public Integer subtract(int baseValue, int difference) {
      * @return difference between `baseValue` and `difference`
      */
     public Long subtract(long baseValue, long difference) {
-        return null;
+        return baseValue - difference;
     }
 
     /**
@@ -83,7 +96,8 @@ public Long subtract(long baseValue, long difference) {
      * @return difference between `baseValue` and `difference`
      */
     public Short subtract(short baseValue, short difference) {
-        return null;
+
+        return (short)(baseValue - difference);
     }
 
     /**
@@ -92,7 +106,8 @@ public Short subtract(short baseValue, short difference) {
      * @return difference between `baseValue` and `difference`
      */
     public Byte subtract(byte baseValue, byte difference) {
-        return null;
+
+        return (byte)(baseValue - difference);
     }
 
     /**
@@ -101,7 +116,8 @@ public Byte subtract(byte baseValue, byte difference) {
      * @return difference between `baseValue` and `difference`
      */
     public Float subtract(float baseValue, float difference) {
-        return null;
+
+        return baseValue - difference;
     }
 
     /**
@@ -110,115 +126,125 @@ public Float subtract(float baseValue, float difference) {
      * @return difference between `baseValue` and `difference`
      */
     public Double subtract(double baseValue, double difference) {
-        return null;
+
+        return baseValue - difference;
     }
 
 
     /**
      * @param dividend value to be divided
-     * @param divisor value to divide by
+     * @param divisor  value to divide by
      * @return division of `dividend` by `divisor
      */
     public Integer divide(int dividend, int divisor) {
-        return null;
+
+        return dividend / divisor;
     }
 
     /**
      * @param dividend value to be divided
-     * @param divisor value to divide by
+     * @param divisor  value to divide by
      * @return division of `dividend` by `divisor
      */
     public Long divide(long dividend, long divisor) {
-        return null;
+
+        return dividend / divisor;
     }
 
     /**
      * @param dividend value to be divided
-     * @param divisor value to divide by
+     * @param divisor  value to divide by
      * @return division of `dividend` by `divisor
      */
     public Short divide(short dividend, short divisor) {
-        return null;
+        return (short)(dividend / divisor);
     }
 
     /**
      * @param dividend value to be divided
-     * @param divisor value to divide by
+     * @param divisor  value to divide by
      * @return division of `dividend` by `divisor
      */
     public Byte divide(byte dividend, byte divisor) {
-        return null;
+        return (byte)(dividend / divisor);
     }
 
     /**
      * @param dividend value to be divided
-     * @param divisor value to divide by
+     * @param divisor  value to divide by
      * @return division of `dividend` by `divisor
      */
     public Float divide(float dividend, float divisor) {
-        return null;
+
+        return dividend / divisor;
     }
 
     /**
      * @param dividend value to be divided
-     * @param divisor value to divide by
+     * @param divisor  value to divide by
      * @return division of `dividend` by `divisor
      */
     public Double divide(double dividend, double divisor) {
-        return null;
+        return dividend / divisor;
     }
 
 
     /**
      * @param multiplicand value to be multiplied
-     * @param multiplier value to multiply by
+     * @param multiplier   value to multiply by
      * @return product of `multiplicand` by `multiplier`
      */
     public Integer multiply(int multiplicand, int multiplier) {
-        return null;
+
+        return multiplicand * multiplier;
     }
 
     /**
      * @param multiplicand value to be multiplied
-     * @param multiplier value to multiply by
+     * @param multiplier   value to multiply by
      * @return product of `multiplicand` by `multiplier`
      */
     public Long multiply(long multiplicand, long multiplier) {
-        return null;
+
+        return multiplicand * multiplier;
     }
 
     /**
      * @param multiplicand value to be multiplied
-     * @param multiplier value to multiply by
+     * @param multiplier   value to multiply by
      * @return product of `multiplicand` by `multiplier`
      */
     public Short multiply(short multiplicand, short multiplier) {
-        return null;
+
+        return (short)(multiplicand * multiplier);
     }
+
     /**
      * @param multiplicand value to be multiplied
-     * @param multiplier value to multiply by
+     * @param multiplier   value to multiply by
      * @return product of `multiplicand` by `multiplier`
      */
     public Byte multiply(byte multiplicand, byte multiplier) {
-        return null;
+        return (byte)(multiplicand * multiplier);
     }
 
     /**
      * @param multiplicand value to be multiplied
-     * @param multiplier value to multiply by
+     * @param multiplier   value to multiply by
      * @return product of `multiplicand` by `multiplier`
      */
     public Float multiply(float multiplicand, float multiplier) {
-        return null;
+
+        return multiplicand * multiplier;
     }
 
     /**
      * @param multiplicand value to be multiplied
-     * @param multiplier value to multiply by
+     * @param multiplier   value to multiply by
      * @return product of `multiplicand` by `multiplier`
      */
     public Double multiply(double multiplicand, double multiplier) {
-        return null;
+
+        return multiplicand * multiplier;
     }
 }
diff --git a/src/main/java/com/zipcodewilmington/danny_do_better_exercises/PredicateUtilities.java b/src/main/java/com/zipcodewilmington/danny_do_better_exercises/PredicateUtilities.java
index cb5f822..d04fe45 100644
--- a/src/main/java/com/zipcodewilmington/danny_do_better_exercises/PredicateUtilities.java
+++ b/src/main/java/com/zipcodewilmington/danny_do_better_exercises/PredicateUtilities.java
@@ -10,7 +10,7 @@ public class PredicateUtilities {
      * @return true if `x` is greater than `y`
      */
     public Boolean isGreaterThan(int x, int y) {
-        return null;
+        if ()
     }
 
     /**
@@ -19,7 +19,10 @@ public Boolean isGreaterThan(int x, int y) {
      * @return true if `x` is less than `y`
      */
     public Boolean isLessThan(int x, int y) {
-        return null;
+        if (x < y) {
+            return true;
+        }
+
     }
 
     /**
diff --git a/src/main/java/com/zipcodewilmington/danny_do_better_exercises/StringUtilities.java b/src/main/java/com/zipcodewilmington/danny_do_better_exercises/StringUtilities.java
index 2f776a9..accef96 100644
--- a/src/main/java/com/zipcodewilmington/danny_do_better_exercises/StringUtilities.java
+++ b/src/main/java/com/zipcodewilmington/danny_do_better_exercises/StringUtilities.java
@@ -8,7 +8,8 @@ public class StringUtilities {
      * @return `Hello World` as a string
      */
     public static String getHelloWorld() {
-        return null;
+
+        return "Hello World";
     }
 
     /**
@@ -17,7 +18,7 @@ public static String getHelloWorld() {
      * @return the concatenation of two strings, `firstSegment`, and `secondSegment`
      */
     public static String concatenation(String firstSegment, String secondSegment){
-        return null;
+        return firstSegment.concat(secondSegment);
     }
 
     /**
@@ -26,7 +27,8 @@ public static String concatenation(String firstSegment, String secondSegment){
      * @return the concatenation of an integer, `firstSegment`, and a String, `secondSegment`
      */
     public static String concatenation(int firstSegment, String secondSegment){
-        return null;
+
+        return firstSegment + secondSegment;
     }
 
     /**
@@ -34,7 +36,7 @@ public static String concatenation(int firstSegment, String secondSegment){
      * @return the first 3 characters of `input`
      */
     public static String getPrefix(String input){
-        return null;
+         return input.substring(0, 2);
     }
 
     /**
@@ -42,7 +44,8 @@ public static String getPrefix(String input){
      * @return the last 3 characters of `input`
      */
     public static String getSuffix(String input){
-        return null;
+        return input.substring(input.length() - 2, input.length());
+
     }
 
     /**
@@ -51,7 +54,8 @@ public static String getSuffix(String input){
      * @return the equivalence of two strings, `inputValue` and `comparableValue`
      */
     public static Boolean compareTwoStrings(String inputValue, String comparableValue){
-        return null;
+            if (inputValue.equals(comparableValue))
+                return true;
     }
 
     /**
@@ -59,7 +63,9 @@ public static Boolean compareTwoStrings(String inputValue, String comparableValu
      * @return the middle character of `inputValue`
      */
     public static Character getMiddleCharacter(String inputValue){
-        return null;
+        int length = inputValue.length();
+        int middle = length / 2;
+        return inputValue.substring(middle); // not sure from here
     }
 
     /**
diff --git a/src/main/java/com/zipcodewilmington/danny_do_better_exercises/ZipcodeRocks.java b/src/main/java/com/zipcodewilmington/danny_do_better_exercises/ZipcodeRocks.java
index 819f21b..fdef5bb 100644
--- a/src/main/java/com/zipcodewilmington/danny_do_better_exercises/ZipcodeRocks.java
+++ b/src/main/java/com/zipcodewilmington/danny_do_better_exercises/ZipcodeRocks.java
@@ -5,6 +5,6 @@
  */
 public class ZipcodeRocks {
     public static void main(String[] args) {
-//         System.out.println("Zipcode Rocks!");
+         System.out.println("Zipcode Rocks!");
     }
 }
diff --git a/src/test/java/com/zipcodewilmington/danny_do_better_exercises/mathutilities/TestAddition.java b/src/test/java/com/zipcodewilmington/danny_do_better_exercises/mathutilities/TestAddition.java
index 03981ff..7ea4bf7 100644
--- a/src/test/java/com/zipcodewilmington/danny_do_better_exercises/mathutilities/TestAddition.java
+++ b/src/test/java/com/zipcodewilmington/danny_do_better_exercises/mathutilities/TestAddition.java
@@ -42,7 +42,7 @@ public void testShortAddition() {
         short addedValue = 7;
         short expected = 16391;
         // : When
-        short actual = mathUtils.add(baseValue, addedValue);
+        short actual = (short) mathUtils.add(baseValue, addedValue);
         // : Then
         assertEquals(expected, actual);
     }