Question

Last week, Ann bought 9 books and 5 movies for a total of $124.

Today, Ann bought 4 books and 21 movies for a total of $318.
Assuming neither item has changed in price, what is the cost of a book in dollars?

Answer 1

$6

Explanation:

Set up a system of equations where b is the cost of a book and m is the cost of a movie:

9b + 5m = 124

4b + 21m = 318

Solve by elimination by multiplying the top equation by -21 and the bottom equation by 5:

-189b - 105m = -2604

20b + 105m = 1590

Add the equations together, then solve for b:

-169b = -1014

b = 6

So, the cost of a book is $6