We know that there are 7 days in a week. Since 57 people rent skates each day, we know that 57*7=399 skates are rented each week. Since one skate cost 4.25, we know that 399*4.25 is the cost, which is 1695.75. (If you are not allowed to use a calculator, you can do 400*4.25-4.25, to make it easier to compute)
