diff --git a/lib/queue.rb b/lib/queue.rb
index 828217c6..34a7834a 100644
--- a/lib/queue.rb
+++ b/lib/queue.rb
@@ -1,28 +1,27 @@
 class Queue
 
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = Array.new
   end
 
   def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+    @store << element
   end
 
   def dequeue
-    raise NotImplementedError, "Not yet implemented"
+    return @store.shift
   end
 
   def front
-    raise NotImplementedError, "Not yet implemented"
+    return @store[0]
   end
 
   def size
-    raise NotImplementedError, "Not yet implemented"
+    return @strore.length
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @store.empty?
   end
 
   def to_s
diff --git a/lib/stack.rb b/lib/stack.rb
index cfc6ef0f..2df0444e 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
   end
 
   def push(element)
-    raise NotImplementedError, "Not yet implemented"
+    @store.add_first(element)
   end
 
   def pop
-    raise NotImplementedError, "Not yet implemented"
+    @store.remove_first
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @store.length == 0
   end
 
   def to_s