Suppose there are x story books, then there are (x+7) comic books and (x- 1 1) science fiction books.

X+7=3(x- 1 1)。

x+7=3x-33

2x= 40

x=20

So the solution of the original equation is x=20.

20+7=27 (Ben)

20- 1 1=9 (Ben)

A: There are 27 comic books, 20 story books and 9 science fiction books.

Pure hands, please adopt.