Distance = 180 miles, Fuel = 15 gallons
If I travel 180 miles and use 15 gallons of gasoline, what is my fuel efficiency in MPG?
To calculate your fuel efficiency in MPG, you need to divide the distance traveled by the amount of fuel used. In your case: 

MPG = 180 miles / 15 gallons = 12 MPG.

Your fuel efficiency is 12 miles per gallon.