The school bought a batch of books, of which literature and art books accounted for 4/9, and mathematics books accounted for 18. There are 20 fewer known math books than literary books. How many books are there?
Let a * * * have x copies!
Literature books =4/9X volumes
Math book =(X-4/9X) 18/25.
Then 4/9X-(X-4/9X) 18/25=20.
4/9X-2/5X=20
2/45X=20
X=450
A: * * * 450!
_ If you are satisfied, please adopt it. thank you