Answer:
A
Find all the volumes
Van: 378 ft³
Small Truck: 648 ft³
Large Truck: 1487.5 ft³
Divide the volumes by the cost
Van Small Truck
378 ÷ 92.50 648 ÷ 162 = 4
4$ per cubic ft 4$ per cubic ft
The small truck is the better deal because you're getting more space for the same price per cubic ft as the moving van.
B
From the volumes we calculated earlier we subtract the volumes: large truck - small truck
1487.5 ft³ - 648 ft³ = 839.5 ft³
C
The family should rent the large truck because it has 1487.5 cubic feet. That is more than enough space than they need.