There are 20 books on literature and art and 5 books on science and technology.

Solution 1: Because the number of literature books is four times that of science and technology books, 25 books can be divided into 5 books; Science and technology books account for 1, and literature and art books account for 4.

Solution 2: Suppose there are X science and technology books, then there are 4x literature books.

x+4x=25

x=5

4x=20