Answer:
15
Explanation:
The volume of the back of his truck is equal to 7.5 X 4 X 8, this equals 240, the volume of each box is 2.5 X 2.5 X 2.5, this equals 15.625, that means that 15.36 boxes fit, but because you can't break a box into .36 pieces, only 15 will fit.