diff --git a/notebooks/pre-algebra/lesson-1.ipynb b/notebooks/pre-algebra/unit1.ipynb
similarity index 91%
rename from notebooks/pre-algebra/lesson-1.ipynb
rename to notebooks/pre-algebra/unit1.ipynb
index 28f9690..40e8487 100644
--- a/notebooks/pre-algebra/lesson-1.ipynb
+++ b/notebooks/pre-algebra/unit1.ipynb
@@ -1,5 +1,14 @@
 {
  "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<a target=\"_blank\" href=\"https://colab.research.google.com/github/rzmk/ladderz/blob/main/notebooks/pre-algebra/unit1.ipynb\">\n",
+    "  <img src=\"https://colab.research.google.com/assets/colab-badge.svg\" alt=\"Open In Colab\"/>\n",
+    "</a>"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},