diff --git a/README.md b/README.md
index 896724c..7494366 100644
--- a/README.md
+++ b/README.md
@@ -41,3 +41,4 @@
 33 / 5 = 6
 84 / 6 = 14
 94 - 31 = 63
+72 - 21 = 51