diff --git a/lib/problems.rb b/lib/problems.rb
index 5085953d..13e0c437 100644
--- a/lib/problems.rb
+++ b/lib/problems.rb
@@ -1,9 +1,21 @@
 require_relative './stack.rb'
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n)
+# Space Complexity: O(n)
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
+  stack = Stack.new
+  string_array = string.split('')
+  pair_hash = { "}" => "{", "]" => "[", ")" => "(" }
+
+  string_array.each do |char|
+    if !pair_hash[char]
+      stack.push(char)
+    elsif stack.pop != pair_hash[char]
+      return false
+    end
+  end
+
+  return stack.empty?
 end
 
 # Time Complexity: ?
diff --git a/lib/queue.rb b/lib/queue.rb
index 828217c6..7c22b71e 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(20)
+    @max_size = 20
+    @front = -1
+    @rear = -1
   end
 
   def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+    if @front == -1
+      @front = 0
+      @rear = 1
+      @store[@front] = element
+
+    elsif @front == @rear
+      raise ArgumentError, "Queue is at max capacity"
+    
+    else
+      @store[@rear] = element
+      @rear = (@rear + 1) % @max_size
+    end
   end
 
   def dequeue
-    raise NotImplementedError, "Not yet implemented"
-  end
+    if @front == -1
+      raise ArgumentError, "Queue is empty"
+    else  
+      element = @store[@front]
+      @front = (@front + 1) % @max_size
 
-  def front
-    raise NotImplementedError, "Not yet implemented"
+      if @front == @rear 
+        @front = @rear = -1 
+      end
+
+      return element
+    end
   end
 
-  def size
-    raise NotImplementedError, "Not yet implemented"
+  def front
+    return @store[@front]
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @front == @rear
   end
 
   def to_s
-    return @store.to_s
+    queue = []
+    current = @front
+    while current != @rear
+      queue << @store[current]
+      current = (current + 1) % @max_size
+    end
+    return queue.to_s
   end
 end
diff --git a/lib/stack.rb b/lib/stack.rb
index cfc6ef0f..f19b42f2 100644
--- a/lib/stack.rb
+++ b/lib/stack.rb
@@ -1,19 +1,18 @@
 class Stack
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = LinkedList.new # using provided Linked List class 
   end
 
   def push(element)
-    raise NotImplementedError, "Not yet implemented"
+    @store.add_last(element)
   end
 
   def pop
-    raise NotImplementedError, "Not yet implemented"
+    return @store.remove_last
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @store.empty?
   end
 
   def to_s
diff --git a/test/problems_test.rb b/test/problems_test.rb
index 046f059e..694262b8 100644
--- a/test/problems_test.rb
+++ b/test/problems_test.rb
@@ -2,7 +2,7 @@
 
 Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
 
-xdescribe "Test wave 3 problems" do
+describe "Test wave 3 problems" do
   describe "balanced" do
     it "Given balanced strings it should return true" do
       
@@ -33,7 +33,7 @@
     end
   end
 
-  describe "postfix" do
+  xdescribe "postfix" do
     it "can add a 2 numbers together" do
       
       expect(evaluate_postfix("34+")).must_equal 7
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 426168c8..f9340080 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -10,4 +10,4 @@
 require_relative "../lib/queue.rb"
 require_relative "../lib/stack.rb"
 # Extra exercises
-# require_relative "../lib/problems.rb"
\ No newline at end of file
+require_relative "../lib/problems.rb"
\ No newline at end of file