diff --git a/lib/problems.rb b/lib/problems.rb
index 5085953d..907eb550 100644
--- a/lib/problems.rb
+++ b/lib/problems.rb
@@ -1,13 +1,68 @@
 require_relative './stack.rb'
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n)
+# Space Complexity: O(n)
+
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
-end
+  # reference https://www.youtube.com/watch?v=0OJdfXyuapc
+  stack = Stack.new
+  parens = string.split('')
+  i = 0
 
-# Time Complexity: ?
-# Space Complexity: ?
-def evaluate_postfix(postfix_expression)
-  raise NotImplementedError, "Not implemented yet"
+  while i < parens.length
+    if (parens[i] == "(" || parens[i] == "{" || parens[i] == "[")
+      stack.push(parens[i])
+    elsif (parens[i] == ")" || parens[i] == "}" || parens[i] == "]")
+      value = stack.pop
+      
+      case parens[i]
+      when ")"
+        if (value == "{" || value == "[")
+          return false
+        end
+      when "}"
+        if (value == "(" || value == "[")
+          return false
+        end
+      when "]"
+        if (value == "(" || value == "{")
+          return false
+        end
+      end
+    end
+    i += 1
+  end
+  return stack.empty? ? true : false
 end
+
+  # keeps giving 5 erros :(
+  # open_parens = [ '(', '[', '{' ]
+  # close_parens = [')', ']', '}' ]
+
+  # check if string length
+  # if string.length % 2 != 0
+  #   return false
+  #   # check if string is empty
+  # elsif string.length == 0
+  #   return true
+  # else
+  #   # check if string starts with a close paren or ends with an open paren (unbalanced)
+  #   if (close_parens.include? string[0]) || (open_parens.include? string[-1])
+  #     return false
+  #   else
+  #     stack = Stack.new
+  #   end
+  # end  
+
+  # string.each_char do |paren|
+  #   if open_parens.include? paren
+  #     stack.push(paren)
+  #     # if paren is a close paren, remove last open paren in stack and check to ensure it's a match for the close paren paren.
+  #   elsif close_parens.include? paren
+  #     last_in_stack = stack.pop()
+  #     if last_in_stack != open_parens[close_parens.index(paren)]
+  #       return false
+  #     end
+  #   end
+  # end
+  # return stack.empty?
diff --git a/lib/queue.rb b/lib/queue.rb
index 828217c6..2fb1739d 100644
--- a/lib/queue.rb
+++ b/lib/queue.rb
@@ -1,31 +1,117 @@
 class Queue
 
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = Array.new(20)
+    @front = -1
+    @back = -1
+    @size = 20
+    # @empty = true
+    # @front = @back = 0
   end
 
   def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+    if ((@front == 0 && @back == @size - 1) || (@back == (( @front - 1) % ( @size - 1))))
+      raise ArgumentError
+    elsif (@front == - 1)
+      @front = 0
+      @back = 0
+      @store[@back] = element
+    elsif ((@back == @size - 1) && (@front != 0))
+      @back = 0
+      @store[@back] = element
+    else
+      @back = @back + 1
+      @store[@back] = element
+    end
+
+    # if @front == @back && !@empty
+    #   raise ArgumentError
+    # else
+    #   @store[@back] = element
+    #   @empty = false
+    #   @back = (@back + 1) % @store.length
+    # end
   end
 
   def dequeue
-    raise NotImplementedError, "Not yet implemented"
+    if (@front == - 1)
+      raise ArgumentError
+    end
+
+    new_queue = @store[@front]
+    @store[@front] = nil
+    
+    if (@front == @back)
+      @front = -1
+      @back = -1
+    elsif (@front == @size - 1 )
+      @front = 0
+    else
+      @front += 1
+    end
+
+    return new_queue
+
+  #  value = @store[@front]
+  #  @store[@front] = nil
+  #  @front = (@front + 1) % @store.length
+
+  #  if @front == @back
+  #   @empty = true
+  #  end
+
+  #  return value
   end
 
   def front
-    raise NotImplementedError, "Not yet implemented"
+    return @store[@front]
   end
 
   def size
-    raise NotImplementedError, "Not yet implemented"
+    if @back < @front
+      count = @size - @front + @back + 1
+    else 
+      count = @back - @front + 1
+    end
+    return count
+
+    # if @front < @back
+    #   return @back - @front
+    # else
+    #   return @back + @store.length - @front
+    # end
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return ((@front == - 1) && (@back == - 1))
+   
+    # return @empty
   end
 
   def to_s
-    return @store.to_s
+
+    if @front == -1 && @back == -1
+      return '[]'
+    elsif @front <= @back
+      return @store[@front..@back].to_s
+    else
+      i = 0
+      index = @front
+      size = @size - @front + @back + 1
+      result = []
+
+      while i < size
+        result << @store[index]
+        if index < @size - 1
+          index += 1
+        else
+          index = 0
+        end
+        i += 1
+      end
+
+      return result.to_s
+    end
   end
+    # return @store.to_s
 end
diff --git a/lib/stack.rb b/lib/stack.rb
index cfc6ef0f..944e38a2 100644
--- a/lib/stack.rb
+++ b/lib/stack.rb
@@ -1,19 +1,23 @@
 class Stack
+
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = LinkedList.new
   end
 
   def push(element)
-    raise NotImplementedError, "Not yet implemented"
+    if @store.nil?
+      @store.add_first(element)
+    else
+      @store.add_last(element)
+    end
   end
 
   def pop
-    raise NotImplementedError, "Not yet implemented"
+    @store.remove_last() unless @store.empty?
   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