Answer:
147 miles, miles = gallons * 21
Explanation:
63 miles on 3 gallons
63 = 3x, where x = miles per gallon
63 = 3x
/3 /3
21 = x, the car gets 21 miles per gallon
y = 7 * 21, where y = miles
y = 147
The car can travel 147 miles with 7 gallons of gas.