diff --git a/lib/problems.rb b/lib/problems.rb
index 5085953d..1aac764a 100644
--- a/lib/problems.rb
+++ b/lib/problems.rb
@@ -3,7 +3,24 @@
 # Time Complexity: ?
 # Space Complexity: ?
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
+  stack = Stack.new
+  pairs = {
+    ')'=> '(',
+    '}'=> '{',
+    ']'=> '['
+  }
+
+  string.each_char do |char|
+    if pairs.values.include?(char)
+      stack.push(char)
+    else
+      return false if stack.empty?
+      removed = stack.pop
+      return false unless removed == pairs[char]
+    end
+  end
+
+  stack.empty? ? true : false
 end
 
 # Time Complexity: ?
diff --git a/lib/queue.rb b/lib/queue.rb
index 828217c6..f921aa47 100644
--- a/lib/queue.rb
+++ b/lib/queue.rb
@@ -1,31 +1,57 @@
 class Queue
 
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = Array.new(30)
+    @front = @back = -1
   end
 
   def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+    if @front == -1 && @back == -1
+      @front = 0
+      @back = 0
+    end
+
+    if ((@back + 1) % @store.length) == @front
+      raise ArgumentError.new "Queue is full"
+    end
+
+    @store[@back] = element
+    @back = (@back + 1) % @store.length
   end
 
   def dequeue
-    raise NotImplementedError, "Not yet implemented"
+    if @front == @back
+      raise ArgumentError.new "Queue is full"
+    end
+
+    temp = @store[@front]
+    @store[@front] = nil
+    @front = (@front + 1) % @store.length
+    return temp
   end
 
   def front
-    raise NotImplementedError, "Not yet implemented"
+    return @store[@front]
   end
 
   def size
-    raise NotImplementedError, "Not yet implemented"
+    if @back.length > @front.length
+      return @back.length - @front.length
+    else
+      return @front.length - @back.length
+    end
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    @front == @back? true : false
   end
 
   def to_s
+    if @front < @back
+      @store = @store[@front...@back]
+    elsif @front != @back
+      @store = @store[@back..-1] + @store[@front...@back]
+    end
     return @store.to_s
   end
 end
diff --git a/lib/stack.rb b/lib/stack.rb
index cfc6ef0f..8d4ddc9d 100644
--- a/lib/stack.rb
+++ b/lib/stack.rb
@@ -1,19 +1,22 @@
+require 'linked_list'
+
 class Stack
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = LinkedList.new
   end
 
   def push(element)
-    raise NotImplementedError, "Not yet implemented"
+    @store.add_last(element)
+    return @store
   end
 
   def pop
-    raise NotImplementedError, "Not yet implemented"
+    return nil if @store.get_first.nil?
+    return @store.remove_last
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return true if @store.get_first.nil?
   end
 
   def to_s
diff --git a/test/problems_test.rb b/test/problems_test.rb
index f851f1d2..546fff53 100644
--- a/test/problems_test.rb
+++ b/test/problems_test.rb
@@ -7,30 +7,25 @@
 describe "Test wave 3 problems" do
   describe "balanced" do
     it "Given balanced strings it should return true" do
-      skip
       expect(balanced('(({}))')).must_equal true
     end
 
     it "regards an empty string as balanced" do
-      skip
       expect(balanced('')).must_equal true
     end
 
     it "will return false for an unbalanced set of parens" do
-      skip
       expect(balanced('(()')).must_equal false
       expect(balanced('(()}')).must_equal false
       expect(balanced('([]]')).must_equal false
     end
 
     it "also works for {} and []" do
-      skip
       expect(balanced('[]')).must_equal true
       expect(balanced('{}')).must_equal true
     end
 
     it "also works if the string has opens and closes in the beginning and end" do
-      skip
       expect(balanced('[]()')).must_equal true
     end
   end
diff --git a/test/queue_test.rb b/test/queue_test.rb
index 8a7dcd9c..6ba1af43 100644
--- a/test/queue_test.rb
+++ b/test/queue_test.rb
@@ -11,14 +11,12 @@
   end
 
   it "adds something to an empty Queue" do
-    skip
     q = Queue.new
     q.enqueue(10)
     q.to_s.must_equal "[10]"
   end
 
   it "adds multiple somethings to a Queue" do
-    skip
     q = Queue.new
     q.enqueue(10)
     q.enqueue(20)
@@ -27,13 +25,11 @@
   end
 
   it "starts the size of a Queue at 0" do
-    skip
     q = Queue.new
     q.empty?.must_equal true
   end
 
   it "removes something from the Queue" do
-    skip
     q = Queue.new
     q.enqueue(5)
     removed = q.dequeue
@@ -42,7 +38,6 @@
   end
 
   it "removes the right something (LIFO)" do
-    skip
     q = Queue.new
     q.enqueue(5)
     q.enqueue(3)
@@ -53,7 +48,6 @@
   end
 
   it "properly adjusts the size with enqueueing and dequeueing" do
-    skip
     q = Queue.new
     q.empty?.must_equal true
     q.enqueue(-1)
@@ -65,7 +59,6 @@
   end
 
   it "returns the front element in the Queue" do
-    skip
     q = Queue.new
     q.enqueue(40)
     q.enqueue(22)
@@ -92,7 +85,6 @@
     q.enqueue(130)
     q.enqueue(140)
     q.enqueue(150)
-    q.enqueue(150)
     q.enqueue(160)
     q.enqueue(170)
     q.enqueue(180)
@@ -101,6 +93,6 @@
     q.enqueue(210)
     q.dequeue
 
-    expect(q.to_s).must_equal('[40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240]')
+    expect(q.to_s).must_equal('[40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210]')
   end
 end
diff --git a/test/stack_test.rb b/test/stack_test.rb
index df5046c8..2cf9d5d9 100644
--- a/test/stack_test.rb
+++ b/test/stack_test.rb
@@ -10,14 +10,12 @@
   end
 
   it "pushes something onto a empty Stack" do
-    skip
     s = Stack.new
     s.push(10)
     s.to_s.must_equal "[10]"
   end
 
   it "pushes multiple somethings onto a Stack" do
-    skip
     s = Stack.new
     s.push(10)
     s.push(20)
@@ -26,13 +24,11 @@
   end
 
   it "starts the stack empty" do
-    skip
     s = Stack.new
     s.empty?.must_equal true
   end
 
   it "removes something from the stack" do
-    skip
     s = Stack.new
     s.push(5)
     removed = s.pop
@@ -41,7 +37,6 @@
   end
 
   it "removes the right something (LIFO)" do
-    skip
     s = Stack.new
     s.push(5)
     s.push(3)