diff --git a/README.md b/README.md
index f153c27..a02f707 100644
--- a/README.md
+++ b/README.md
@@ -41,3 +41,4 @@
 43 + 30 = 73
 53 / 8 = 6
 89 + 61 = 150
+13 - 20 = -7