First, you do 330 divided by 15 to find the unit rate and that will be 22
Then, you do 22 times 5 since 15+5=20 and you will get 110
Last, do 110+330 since 330 is 15 miles and 110 is 5 miles and you will get 440
So, your answer is 440 miles using 20 gallons of gas