diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..dec81dc 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -16,40 +16,104 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n)
+  # Space Complexity: O(n)
   def add(key, value)
-    raise NotImplementedError
+    new_node = TreeNode.new(key, value)
+
+    if @root.nil?
+      @root = new_node
+    else
+      add_helper(@root, new_node)
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def add_helper(current, new_node)
+    return new_node if current.nil?
+
+    if new_node.key <= current.key
+      current.left = add_helper(current.left, new_node)
+    else
+      current.right = add_helper(current.right, new_node)
+    end
+
+    return current
+  end
+
+  # Time Complexity: O(log n)
+  # Space Complexity: O(log n)
   def find(key)
-    raise NotImplementedError
+    find_helper(key, @root)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def find_helper(key, current)
+    return nil if current.nil?
+
+    if current.key == key
+      return current.value
+    elsif current.key > key
+      find_helper(key, current.left)
+    elsif current.key < key
+      find_helper(key, current.right)
+    end
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def inorder
-    raise NotImplementedError
+    inorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def inorder_helper(current, values)
+    return values if current.nil?
+    
+    inorder_helper(current.left, values)
+    values << { key: current.key, value: current.value }
+    inorder_helper(current.right, values)
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def preorder
-    raise NotImplementedError
+    return preorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def preorder_helper(current, values)
+    return values if current.nil?
+
+    values << { key: current.key, value: current.value }
+    preorder_helper(current.left, values)
+    preorder_helper(current.right, values)
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def postorder
-    raise NotImplementedError
+    return postorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def postorder_helper(current, values)
+    return values if current.nil?
+    
+    postorder_helper(current.left, values)
+    postorder_helper(current.right, values)
+    values << { key: current.key, value: current.value }
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def height
-    raise NotImplementedError
+    return height_helper(@root)
+  end
+
+  def height_helper(current)
+    return 0 if current.nil?
+
+    if current
+      left_height = 1 + height_helper(current.left)
+      right_height = 1 + height_helper(current.right)
+      return left_height > right_height ? left_height : right_height
+    end
   end
 
   # Optional Method
diff --git a/test/tree_test.rb b/test/tree_test.rb
index 60f5981..21d1b41 100644
--- a/test/tree_test.rb
+++ b/test/tree_test.rb
@@ -91,7 +91,7 @@
     it "will return 1 for a tree of height 1" do
       my_tree = Tree.new
 
-      my_tree.add(100)
+      my_tree.add(100, 1)
       expect(my_tree.height).must_equal 1
     end
 
@@ -102,11 +102,11 @@
     it "will report the height for unbalanced trees" do
       my_tree = Tree.new
 
-      my_tree.add(100)
-      my_tree.add(110)
-      my_tree.add(120)
-      my_tree.add(130)
-      my_tree.add(140)
+      my_tree.add(100, 1)
+      my_tree.add(110, 1)
+      my_tree.add(120, 1)
+      my_tree.add(130, 1)
+      my_tree.add(140, 1)
 
       expect(my_tree.height).must_equal 5
 
@@ -114,11 +114,11 @@
 
       my_tree = Tree.new
 
-      my_tree.add(100)
-      my_tree.add(90)
-      my_tree.add(80)
-      my_tree.add(70)
-      my_tree.add(60)
+      my_tree.add(100, 1)
+      my_tree.add(90, 1)
+      my_tree.add(80, 1)
+      my_tree.add(70, 1)
+      my_tree.add(60, 1)
 
       expect(my_tree.height).must_equal 5
     end