Update Day_13.md

Author: darkprinx

Status/Day_13.md

@@ -140,3 +140,5 @@ print(Square().area()) # prints zero as default area
 ## Conclusion
 
 ***Well It seems that the above problems are very much focused on basic concpets and implimantation of object oriented programming.As the concepts are not about to solve any functional problem rather design the structure , so both codes are very much similar in there implimantation part.***
+
+[***go to previous day***](https://github.com/darkprinx/100-plus-Python-programming-exercises-extended/blob/master/Status/Day_12.md "Day 12")