Question 314090
Let city driving be x miles.
highway driving = 4 times city driving =4x
5x=300
x=60 city driving.
highway driving = 240 miles.
..
20 mpg in city. 
in city 60 /20 = 3 gallons.
..
240 miles on highway.
30 mpg. 
On highway 240/30 = 8 gallons
..
Total gas = 11 gallons