26 gallons
1) We can write this information setting up a proportion
miles gallons
120 10
312 x
2) Assuming the pace hasn't changed, then we can consider that as proportional:
120x = 312 * 10
120x= 3120
x = 3120/120
x =26
3) So 26 gallons are going to be needed for those 312 miles.
