Merge pull request lydiahallie#30 from patrix252/patch-1

Fix the question 21

Author: lydiahallie

README.md

@@ -629,7 +629,7 @@ With `"use strict"`, you can make sure that you don't accidentally declare globa
 
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-###### 21. What's the output?
+###### 21. What's value of `sum`?
 
 ```javascript
 const sum = eval("10*10+5");