diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..4afb8d3 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -14,42 +14,121 @@ class Tree
   attr_reader :root
   def initialize
     @root = nil
+    @nodes = []
+  end
+
+  def add_helper(current, key)
+    if key <= current.key
+      return current if current.left.nil?
+      add_helper(current.left, key)
+    else
+      return current if current.right.nil?
+      add_helper(current.right, key)
+    end
   end
 
   # Time Complexity: 
   # Space Complexity: 
   def add(key, value)
-    raise NotImplementedError
+    if @root == nil
+      @root = TreeNode.new(key, value)
+      return
+    end
+
+    node = add_helper(@root, key)
+    if key <= node.key
+      node.left = TreeNode.new(key, value)
+    else
+      node.right = TreeNode.new(key, value)
+    end
+  end
+
+  def find_helper(current, key)
+    if key <= current.key
+      return current.value if current.key == key
+      find_helper(current.left, key)
+    elsif key > current.key
+      return current.value if current.key == key
+      find_helper(current.right, key)
+    end
   end
 
   # Time Complexity: 
   # Space Complexity: 
   def find(key)
-    raise NotImplementedError
+    return nil if @root.nil?
+    return @root.value if @root.key == key
+
+    current = @root
+    find_key = find_helper(current, key)
+
+    return find_key
+  end
+
+  # inorder helper
+  def traverse_inorder(tree)
+    traverse_inorder(tree.left) if tree.left
+    @nodes.push({key: tree.key, value: tree.value})
+    traverse_inorder(tree.right) if tree.right
   end
 
   # Time Complexity: 
   # Space Complexity: 
+  # left, root, right
   def inorder
-    raise NotImplementedError
+    return [] if @root.nil?
+    traverse_inorder(@root)
+    return @nodes
   end
 
+  # preorder helper
+  def traverse_preorder(tree)
+    @nodes.push({key: tree.key, value: tree.value})
+    traverse_preorder(tree.left) if tree.left
+    traverse_preorder(tree.right) if tree.right
+  end  
+
   # Time Complexity: 
   # Space Complexity: 
   def preorder
-    raise NotImplementedError
+    return [] if @root.nil?
+    traverse_preorder(@root)
+    return @nodes
   end
 
+  # postorder helper
+  def traverse_postorder(tree)
+    traverse_postorder(tree.left) if tree.left
+    traverse_postorder(tree.right) if tree.right
+    @nodes.push({key: tree.key, value: tree.value})
+  end  
+
   # Time Complexity: 
   # Space Complexity: 
   def postorder
-    raise NotImplementedError
+    return [] if @root.nil?
+    traverse_postorder(@root)
+    return @nodes
+  end
+
+  def height_helper(tree, height)
+    return height_helper(tree.left, height) if tree.left
+    return height_helper(tree.right, height) if tree.right
+    return height + 1
   end
 
   # Time Complexity: 
   # Space Complexity: 
   def height
-    raise NotImplementedError
+    return 0 if @root.nil?
+    return 1 if (@root.left.nil? && @root.right.nil?)
+
+    left_height = 1
+    height_helper(@root.left, 1) if @root.left
+    right_height = 1
+    height_helper(@root.right, 1) if @root.right
+
+    return left_height >= right_height ? left_height : right_height
   end
 
   # Optional Method
diff --git a/test/tree_test.rb b/test/tree_test.rb
index 21c4a80..1f45c90 100644
--- a/test/tree_test.rb
+++ b/test/tree_test.rb
@@ -34,6 +34,16 @@
 
     tree.add(3, "Paul")
     expect(tree.find(3)).must_equal "Paul"
+
+    tree.add(4, "Mary")
+    expect(tree.find(4)).must_equal "Mary"
+
+    tree.add(10, "Karla")
+    expect(tree.find(10)).must_equal "Karla"
+
+    tree.add(1, "Jenny")
+    expect(tree.find(1)).must_equal "Jenny"
+
   end
 
   it "can't find anything when the tree is empty" do
@@ -49,6 +59,15 @@
       expect(tree_with_nodes.inorder).must_equal [{:key=>1, :value=>"Mary"}, {:key=>3, :value=>"Paul"}, 
                                        {:key=>5, :value=>"Peter"}, {:key=>10, :value=>"Karla"}, 
                                        {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
+      expect(balanced_tree.inorder).must_equal [
+        {:key=>1, :value=>"Mary"}, 
+        {:key=>3, :value=>"Paul"}, 
+        {:key=>4, :value=>"Kate"},
+        {:key=>5, :value=>"Peter"}, 
+        {:key=>8, :value=>"Ada"},
+        {:key=>10, :value=>"Karla"}, 
+        {:key=>25, :value=>"Kari"}
+      ]
     end
   end