The number of science and technology books in the school library is three times less than that of story books, with 30 books. There are 525 science books, and how many story books are there?
Formula:
(525+30)/3= 185 copies
Equation: suppose there are x story books.
3x-30=525
3x=525+30
x=555/3
X= 185 copies
A: There are 185 story books.