Question

HELP! Please explain how to do this!

Answer 1

$45 paid first, then marked it up by 15%:
$45 x 1.5 = $67.50

To find 36% of $67.50:
X/67.50 = 36/100 (cross multiply)
67.50 x 36 = 2430
X(100) = 100X
2430 divided by 100 = 24.30

He spent $24.30 on books! (36%)