A has 13% professional books. In order to make the number of specialized books in A an integer, A must be 100 or 200 (only in these two cases, because books cannot be divided into decimals. )
If A has 200 copies and B has 60 copies, 60 times 1/8 is not an integer. So this doesn't hold. (Note: 12.5% decreased to 1/8)
So it can only be: A is 100, in which 13% is professional and 1- 13% is unprofessional = 87%.
100 times 87%=87 copies.