Step-by-step explanation:
Percentage by which the gas tank of the car is full = 40%
Amount of gas in the gas tank = 8 gallons
capacity of the gas tank = x gallons
40% * x = 8
(40/100) * x = 8
4x/10 = 8
4x = 8 * 10
4x = 80
x = 80/4
Answer = 20 gallons
