Answer:
On the 4th day, the sum of penalties and charges will be the same in both the school library and the town library.
Explanation:
School library
Penalty-25
Every day charge-5
City library
Penalty-5
Every day charge-10
Let the day when total fee at both libraries will be same be x
Total charge in school library-25+5x
Total charge in city library-5+10x
They both amount to be equal