Someone already got the answer, I think but here's an explanation on how to get it ig?
Get the miles traveled from the trip odometer, or subtract the original odometer reading from the new one.
Divide the miles traveled by the amount of gallons it took to refill the tank. The result will be your car's average miles per gallon yield for that driving period.
To find the unit rate which is 1/8 we just divide 15 by 3 which is 5 and to find the mpg of the full gallon now that we have the unit rate we just multiply the 1/8 or 5 miles by 8 which would give us 8/8 or 40 miles.
