Question

$12 for 3 paperback books;$28 for 7 paperback book

Answer 1

so assuming to solve for rate
12 for 3
divide
12/3=4
$4 per 1 book

28 for 7
divide
28/7=4
$4 per book

the rate is $4 per paperback book

Answer 2

12/3=4
28/7=4
So 4$ for a paperback book.