Update README.md

dmalan · web-flow · commit bc4613e632c6 · 2017-10-22T19:20:40.000-04:00
diff --git a/README.md b/README.md
@@ -17,9 +17,10 @@
 ### Ubuntu
 
 ```
-$ sudo apt-add-repository ppa:cs50/ppa
-$ sudo apt-get update
-$ sudo apt-get install libcs50
+sudo apt-get install software-properties-common
+sudo apt-add-repository ppa:cs50/ppa
+sudo apt-get update
+sudo apt-get install libcs50
 ```
 
 ### From Source (Linux and Mac)
