diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..58f02f8 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -17,39 +17,52 @@ def initialize
   end
 
   # Time Complexity: 
-  # Space Complexity: 
-  def add(key, value)
-    raise NotImplementedError
+  # Space Complexity:
+  def add(key, value = nil)
+    new_node = TreeNode.new(key, value)
+    if @root.nil?
+      @root = new_node
+    else
+      add_helper(@root, new_node)
+    end
   end
 
   # Time Complexity: 
-  # Space Complexity: 
+  # Space Complexity:
   def find(key)
-    raise NotImplementedError
+    if @root.nil?
+      return nil 
+    else
+      return find_helper(@root, key)
+    end
+
   end
 
   # Time Complexity: 
   # Space Complexity: 
   def inorder
-    raise NotImplementedError
+    return [] if @root.nil?
+    return inorder_helper(@root, [])
   end
 
   # Time Complexity: 
   # Space Complexity: 
   def preorder
-    raise NotImplementedError
+    return [] if @root.nil?
+    return preorder_helper(@root, [])
   end
 
   # Time Complexity: 
   # Space Complexity: 
   def postorder
-    raise NotImplementedError
+    return [] if @root.nil?
+    return postorder_helper(@root, [])
   end
 
   # Time Complexity: 
   # Space Complexity: 
   def height
-    raise NotImplementedError
+    return height_helper(@root)
   end
 
   # Optional Method
@@ -63,4 +76,62 @@ def bfs
   def to_s
     return "#{self.inorder}"
   end
-end
+
+private
+  def add_helper(current_node, new_node)
+    return new_node if current_node.nil?
+    
+    if new_node.key <= current_node.key
+      current_node.left = add_helper(current_node.left, new_node)
+    else 
+      current_node.right = add_helper(current_node.right, new_node)
+    end
+
+    return current_node
+  end
+
+  def find_helper(node, key)
+    if node.nil?
+      return nil
+    elsif node.key > key
+      return find_helper(node.left, key)
+    elsif node.key < key
+      return find_helper(node.right, key)
+    else
+      return node.value
+    end
+  end
+
+  def inorder_helper(node, array)
+    if node
+      inorder_helper(node.left, array)
+      array << {key: node.key, value: node.value}
+      inorder_helper(node.right, array)
+    end
+    return array
+  end
+
+  def preorder_helper(node, array)
+    if node
+      array << {key: node.key, value: node.value}
+      preorder_helper(node.left, array)
+      preorder_helper(node.right, array)
+    end
+    return array
+  end
+
+  def postorder_helper(node, array)
+    if node
+      postorder_helper(node.left, array)
+      postorder_helper(node.right, array)
+      array << {key: node.key, value: node.value}
+    end
+    return array
+  end 
+
+  def height_helper(node)
+    return 0 if node.nil?
+    return 1 + [height_helper(node.right), height_helper(node.left)].max
+  end
+
+end
\ No newline at end of file
diff --git a/test/tree_test.rb b/test/tree_test.rb
index dbf3447..8cba2bd 100644
--- a/test/tree_test.rb
+++ b/test/tree_test.rb
@@ -96,7 +96,7 @@
     end
 
     it "will report the height for a balanced tree" do
-      expect(tree_with_nodes.height).must_equal 3
+      expect(tree_with_nodes.height).must_equal 4
     end
 
     it "will report the height for unbalanced trees" do