Your chemistry textbook has 936 pages and weighs 4.2 pounds. your calculus textbook has 1368 pages and weighs 6.0 pounds. these books ship in cases that hold 24 books each. a shipment of 20 cases of books that weighs 2707.2 pounds arrives at the bookstore. how many cases of chemistry books are there in this shipment? report your answer to the nearest whole number.

Let the number of chemistry books be x and the number of calculus books be y
total number of books in each case is:
x+y=24
x=24-yi

Weight of each case:
2707.2/20
=135.36
thus
4.2x+6.0y=135.36..ii substituting i in ii
4.2(24-y)+6y=135.36
100.8-4.2y+6y=135.36
hence
1.8y=34.56
y=19.2
hence
x=24-19.2
x=4.8
thus the number of chemistry books was 4.8*20=96 number of calculus was
19.2*20
=384 books