The ratio given is 3:7 where nonfiction:fiction.
To find the new ratio, divide 3 from 240.
240 / 3 = 80
Now multiply 80 by 7.
80 x 7 = 560
The new ratio is 240:560
If there are 240 nonfiction books then there are 560 fiction books.
To find the total, add these together.
240 + 560 = 800
There are 800 total books