typo

Author: chentsulin

problems/basic_filter/problem.md

@@ -16,7 +16,7 @@ Use Array#filter to write a function called `getShortMessages`.
 ## Conditions
 
 * Do not use any for/while loops or Array#forEach.
-* Do not create any unecessary functions e.g. helpers.
+* Do not create any unnecessary functions e.g. helpers.
 
 ## Hint