If the books in the upper layer are taken out 10 1 and placed in the lower layer, and the two layers of books are equal, then there are more books in the upper layer than in the lower layer.

10 1*2=202 (Ben)

Suppose there are X books in the lower level, then there are 3X+ 18 books in the upper level.

3X+ 18-X = 10 1 * 2

The solution is X=92.

3X+ 18=3*92+ 18=294

2.8*(x-2)=2*(x+7)

8x- 16=2x+ 14

6x=30

x=5