Question

A radio station gave away concert tickets every hour yesterday. At the end of the fourth hour, the station had 540 tickets left. At the end of the eighth hour, the station had 432 tickets left.

Write an equation in general form that expresses the number of tickets left at the radio station, y, as a function of the number of hours past, x
27x + y = 648
27x - y = -216
27x + y = 216
27x - y = 648