Question

The Hydro water department has a monthly service charge of $13.50 and a volume charge of $2.01 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 = 2.01x + 13.50

If the Johnson family used 300 ft3 less water this month than last month, then they can expect

Answer 1

y2=2.01x2 + 13.50
y1=2.01x1 + 13.50
x2-x1=300