With x peach trees and 3/5x pear trees, x+3/5x= 160, the result is x= 100.

So there are 100 peach trees and 60 pear trees.

If there are x reference books and y science and technology books, then y=( 180-y)* 1/2 gives y=60, and literature books have (x+60) *1/5 =180-x-60.

The solution is x = 90.

So there are 90 reference books.