20% of the books in a library are fiction. and the rest are non fiction. When 30% of the fiction books and 15% of the non fiction books are borrowed there are 1,312 books left in the library. How many books are borrowed?

Answer 1

If there are x books, then
f = 0.2x
n = 0.8x
x - 0.30f - 0.15n = 1312

so, now find x, and then figure out how many are borrowed.