A mail order catalog lists books for 3x - 5 dollars each. The cost of postage is $2 for 3 books or less. Represent the cost of an order for 5 books.

the cost of an order for 5 books=15x-21

Step-by-step explanation:

a mail order catalog lists books for 3x - 5 dollars each.

i. e. cost of 1 book=3x-5

Hence, cost of 5 books=5 * (3x-5) = $ (15x-25)

also the cost of postage is $2 for 3 books or less.

as there are 5 books so we have to make two postages.

Hence, cost of postage for 5 books=$4

Hence, the total cost of an order of 5 books=15x-25+4

=15x-21.