Update Day_12.md

Author: darkprinx

Status/Day_12.md

@@ -17,6 +17,11 @@ print squaredNumbers
 ----------------
 **My Solution: Python 3**
 ```
+def sqr(x):
+ return x*x
+
+squaredNumbers = list(map(sqr, range(1,21)))
+print (squaredNumbers)
 ```
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