Arental company charges a flat fee of x dollars for a floor sander rental plus y dollars per hour of rental. one customer rents a floor sander for 4 hours and pays $63. another rents a floor sander for 6 hours and pays $87. find the flat fee and the cost per hour for the rental.

Take 87-63 = 24, which is the difference of the 2 hours. Divide this by two to get the hourly rate, which is $12.

We can now set up the equation as follows:
4(12) + x = 63
6(12) + x = 87

Now solve for each:
4(12) + x =63
48 + x = 63
x = $15

6(12) + x = $87
72 + x = 87
x = $15

Therefore, the Flat Fee = $15 and the Hourly rate = $12 

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