Math
posted by Jeanifer .
A movie theater sold a total of 390 adult and child tickets on a certain day. The theater sold 2.25 times as many adult tickets as child tickets. Each adult ticket cost $8 and each child ticket cost $3. How much revenue did the theater generate in ticket sales that day?

a + c = 390
a = 2.25 c
so 2.25 c + 1 c = 390, solve for c then for a
Revenue = 8 a + 3 c