If you would like to know the percent of the missing order, you can calculate this using the following steps:
800 books - 160 books = 640 missing books
x% of 800 art books is 640 missing books
x% * 800 = 640
x/100 * 800 = 640
x * 8 = 640 /8
x = 640/8
x = 80%
The correct result would be: 80% missing books.
