Respuesta :

Answer:

he could drive 4 hours

Step-by-step explanation:

Step-by-step explanation:

if he drives for 1 hour he will have 21 gallons left

2 hours = 15 gallons left

3 hours = 9 gallons left

4 hours = 3 gallons left

4.5 hours = 0 gallons left

he could drive a total of 4.5 hours before he runs out of gas