Method 1:

Solution: If there are N books in the lower level and 4n books in the upper level.

4n-60=n+60

3n = 120

n=40

Upper layer: 40*4= 160 (Ben)

A: There are 160 books upstairs and 40 books downstairs.

Method 2:

Difference between upper and lower floors: 60+60= 120 (Ben)

Multiply of the difference between upper and lower floors: 4- 1=3 (times)

Lower level: 120/3=40 (Ben)

Lower floor: 40*4= 160 (Ben)