diff --git a/challenges/classes.js b/challenges/classes.js
index 992e39dc0b..f9826d1d20 100644
--- a/challenges/classes.js
+++ b/challenges/classes.js
@@ -1,7 +1,23 @@
 // 1. Copy and paste your prototype in here and refactor into class syntax.
 
+class CuboidMaker {
+  constructor(length, width, height) {
+      this.length = length;
+      this.width = width;
+      this.height = height;
+  }
+  volume() {
+      return this.length * this.width * this.height;
+  }
+  surfaceArea() {
+      return 2 * (this.length * this.width + this.length * this.height + this.width * this.height);
+  }
+}
+
+let cuboid = new CuboidMaker(4, 5, 5);
+
 // Test your volume and surfaceArea methods by uncommenting the logs below:
-// console.log(cuboid.volume()); // 100
-// console.log(cuboid.surfaceArea()); // 130
+console.log(cuboid.volume()); // 100
+console.log(cuboid.surfaceArea()); // 130
 
 // Stretch Task: Extend the base class CuboidMaker with a sub class called CubeMaker.  Find out the formulas for volume and surface area for cubes and create those methods using the dimension properties from CuboidMaker.  Test your work by logging out your volume and surface area.
\ No newline at end of file
diff --git a/challenges/functions.js b/challenges/functions.js
index 6e3688bfcc..546bec5970 100644
--- a/challenges/functions.js
+++ b/challenges/functions.js
@@ -7,6 +7,9 @@
   * The consume function should return the invocation of cb, passing a and b into cb as arguments
 */
 
+function consume(a, b, cb) {
+  return cb(a, b);
+}
 
 /* Step 2: Create several functions to callback with consume();
   * Create a function named add that returns the sum of two numbers
@@ -14,11 +17,22 @@
   * Create a function named greeting that accepts a first and last name and returns "Hello first-name last-name, nice to meet you!"
 */
 
+function add(num1, num2) {
+  return num1 + num2;
+}
+
+function multiply(num1, num2) {
+  return num1 * num2;
+}
+
+function greeting(firstName, lastName) {
+  return `Hello ${firstName} ${lastName}, nice to meet you!`;
+}
 
 /* Step 3: Check your work by un-commenting the following calls to consume(): */
-// console.log(consume(2, 2, add)); // 4
-// console.log(consume(10, 16, multiply)); // 160
-// console.log(consume("Mary", "Poppins", greeting)); // Hello Mary Poppins, nice to meet you!
+ console.log(consume(2, 2, add)); // 4
+ console.log(consume(10, 16, multiply)); // 160
+ console.log(consume("Mary", "Poppins", greeting)); // Hello Mary Poppins, nice to meet you!
 
 
 // ==== Closures ==== 
@@ -26,6 +40,7 @@
 // Explain in your own words why nestedfunction can access the variable internal.
 
 // Explanation: 
+// Functions can reach outward an access outside functions (but never inward).
 
 
 const external = "I'm outside the function";
diff --git a/challenges/objects-arrays.js b/challenges/objects-arrays.js
index 659e3e149c..1ed6a02ebf 100644
--- a/challenges/objects-arrays.js
+++ b/challenges/objects-arrays.js
@@ -8,27 +8,51 @@
 
 // tyrannosaurus, carnivorous, 7000kg, 12m, Late Cretaceous
 
+let tyrannosaurus = {
+  diet: "carnivorous",
+  weight: "7000kg",
+  length: "12m",
+  period: "Late Cretaceous",
+  roar: function() {
+    return "RAWERSRARARWERSARARARRRR!";
+  }
+};
+
 // stegosaurus, herbivorous, 2000kg, 9m, Late Jurassic
 
+let stegosaurus = {
+  diet: "herbivorous",
+  weight: "2000kg",
+  length: "9m",
+  period: "Late Jurassic"
+};
+
 // velociraptor, carnivorous, 15kg, 1.8m, Late Cretaceous
 
+let velociraptor = {
+  diet: "carnivorous",
+  weight: "15kg",
+  length: "1.8m",
+  period: "Late Cretaceous"
+};
+
 // Using your dinosaur objects, log answers to these questions:
 
 // How much did tyrannosaurus weigh?
-console.log();
+console.log(tyrannosaurus.weight);
 
 // What was the diet of a velociraptor?
-console.log();
+console.log(velociraptor.diet);
 
 // How long was a stegosaurus?
-console.log();
+console.log(stegosaurus.length);
 
 // What time period did tyrannosaurus live in?
-console.log();
+console.log(tyrannosaurus.period);
 
 
 // Create a new roar method for the tyrannosaurus.  When called, return "RAWERSRARARWERSARARARRRR!" Log the result.
-console.log();
+console.log(tyrannosaurus.roar());
 
 
 // ==== Arrays ====
@@ -52,6 +76,8 @@ const graduates = [
 
 Once you have the new array created, sort the universities alphabetically and log the result. */
 const universities = [];
+graduates.forEach(element => universities.push(element.university));
+universities.sort();
 console.log(universities);
 
 /* Request 2: Create a new array called contactInfo that contains both first name and email of each student. This will be an array of strings.
@@ -61,10 +87,12 @@ The resulting contact information strings should have a space between the first
 
 Log the result of your new array. */
 const contactInfo = [];
+graduates.forEach(element => contactInfo.push(`${element.first_name} ${element.email}`));
 console.log(contactInfo);
 
 /* Request 3: Find out how many universities have the string "Uni" included in their name. Create a new array called unisWithUni that contains them all. This will be an array of objects. Log the result. */
 const unisWithUni = [];
+graduates.forEach(element => element.university.includes("Uni") && unisWithUni.push(element));
 console.log(unisWithUni);
 
 
@@ -91,6 +119,7 @@ The zoos want to display both the scientific name and the animal name in front o
 
 */
 const displayNames = [];
+zooAnimals.forEach(element => displayNames.push(`Name: ${element.animal_name}, Scientific: ${element.scientific_name}`));
 console.log(displayNames);
 
 /* Request 2: .map()
@@ -99,7 +128,7 @@ The zoos need a list of all their animal's names (animal_name only) converted to
 
 */
 
-const lowCaseAnimalNames = [];
+const lowCaseAnimalNames = zooAnimals.map(element => element.animal_name.toLowerCase());
 console.log(lowCaseAnimalNames);
 
 /* Request 3: .filter() 
@@ -107,7 +136,7 @@ console.log(lowCaseAnimalNames);
 The zoos are concerned about animals with a lower population count. Using filter, create a new array of objects called lowPopulationAnimals which contains only the animals with a population less than 5.
 
 */
-const lowPopulationAnimals = [];
+const lowPopulationAnimals = zooAnimals.filter(element => element.population < 5);
 console.log(lowPopulationAnimals);
 
 /* Request 4: .reduce() 
@@ -115,9 +144,11 @@ console.log(lowPopulationAnimals);
 The zoos need to know their total animal population across the United States. Find the total population from all the zoos using the .reduce() method. Remember the reduce method takes two arguments: a callback (which itself takes two args), and an initial value for the count.
 
 */
-const populationTotal = 0;
-console.log(populationTotal);
+const reducer = (accumulator, currentValue) => accumulator + currentValue.population;
+
+const populationTotal = zooAnimals.reduce(reducer, 0);
 
+console.log(populationTotal);
 
 /*
 
diff --git a/challenges/prototypes.js b/challenges/prototypes.js
index 4cafc33e95..9938330d29 100644
--- a/challenges/prototypes.js
+++ b/challenges/prototypes.js
@@ -6,6 +6,11 @@
   Create a constructor function named CuboidMaker that accepts properties for length, width, and height
 */
 
+function CuboidMaker(length, width, height) {
+  this.length = length;
+  this.width = width;
+  this.height = height;
+}
 
 /* == Step 2: Volume Method ==
   Create a method using CuboidMaker's prototype that returns the volume of a given cuboid's length, width, and height
@@ -13,6 +18,9 @@
   Formula for cuboid volume: length * width * height
 */
 
+CuboidMaker.prototype.volume = function() {
+  return this.length * this.width * this.height;
+}
 
 /* == Step 3: Surface Area Method ==
   Create another method using CuboidMaker's prototype that returns the surface area of a given cuboid's length, width, and height. 
@@ -20,14 +28,19 @@
   Formula for cuboid surface area of a cube: 2 * (length * width + length * height + width * height)
 */
 
+CuboidMaker.prototype.surfaceArea = function() {
+  return 2 * (this.length * this.width + this.length * this.height + this.width * this.height);
+}
 
 /* == Step 4: Create a new object that uses CuboidMaker ==
   Create a cuboid object that uses the new keyword to use our CuboidMaker constructor
   Add properties and values of length: 4, width: 5, and height: 5 to cuboid.   
 */
 
+let cuboid = new CuboidMaker(4, 5, 5);
+
 // Test your volume and surfaceArea methods by uncommenting the logs below:
-// console.log(cuboid.volume()); // 100
-// console.log(cuboid.surfaceArea()); // 130
+console.log(cuboid.volume()); // 100
+console.log(cuboid.surfaceArea()); // 130