A company sells used tires at $25.00 and new tiress at $50.00.  In one month the total combined sales was $28,125.  Customers bought 4 times as many new tires as used.  How many of each item was sold last month?

Ley x, y  be the used  tyres amd new tyres.

4x=y.

25x+50y=28125.

25x+50*4x=28125.

x=28125/225.

=125.

y=4x=125*4.

=500.

Number of new tyres y=500.

Number of used tyres x=125.