The Hydro water department has a monthly service charge of $12.90 and a volume charge of $1.67 for every 100 cubic feet of water. The total monthly cost is equal to the service charge plus the charge for the volume used during the month. If we let x represent the number of cubic feet of water (in hundreds) and y represent the total monthly cost, then we have: total monthly cost = volume charge + service charge y = 1.67x + 12.90 If the Johnson family used 200 ft3 more water this month than last month, then they can expect