A family has two cars. the first car has a fuel efficiency of 20 miles per gallon of gas and the second has a fuel efficiency of 25 miles per gallon of gas. during one particular week, the two cars went a combined total of 775 miles, for a total gas consumption of 35 gallons. how many gallons were consumed by each of the two cars that week?
Let's call the fuel consumption of the first car "x" and the second car "y" x + y = 35 is the total fuel consumed. 20x + 25y = 775 is the distance traveled. Solve the two equations. Skipping a few steps, I get 5y = 75. Therefore y = 15. So y used 15 gallons of gas. Therefore x used 20 gallons.
