If you cross mulitply the answer would be 13.3
The answer I got was C = The car used 70 gallons of gas to go 3 miles.
Hope this helps.
The hexagonal prism has a an equation of volume = base * height.
Since we already know the base is 8 sq feet, we can plug in some values and use x as a missing value
40 = 8 * x
Divide by 8
5 = x
X is equal to 5.
Hm, it seems like his answer is off. The image is what I got.