Mickey bought 3 books from the bargain bin at his school's book fair and paid six dollars. If buying books from the bargain bin follows a direct variation, how much did his sister pay for the 4 books she bought?
$6 / 2 b00ks = $2. / book.
C = kx = 2x = Direct variation.
C = 2x = 2 * 4 = $8 = Cost of Mickey's sister's books.