The pints of paint that Mike needs to buy in order to paint 4 boxes is 9 pints.
The first step is determine the total surface area of a box.
Total surface area of a cuboid = 2 (lw + wh + lh)
where:
2 x[ (5 x 9/2) + (9/2 x 7/2) + (5 x 7/2) ]
2 x ( 45/2 + 63/4 + 35/2) = 111.5ft
The second step is to determine the total surface area of 4 boxes:
111.5 x 4 = 446
Now, divide 446 by 50
446 / 50 = 9 pints
To learn more about a cuboid, please check: https://brainly.com/question/26406747