Atheater charges $50 per ticket for seats in section a, $40 per ticket for seats in section b, and $20 per ticket for seats in section c. for one play, 9,500 tickets were sold for a total of $335,000 in revenue. if 500 more tickets in section b were sold than the other two sections combined, how many tickets in each section were sold?

The first thing we must do for this case is to define variables.
 We have then:
 x: ticket for seats in section a
 y: ticket for seats in section b
 z: ticket for seats in section c
 We write the system of equations:
 50x + 40y + 20z = 335000
 x + y + z = 9500
 y = x + z + 500
 Solving the system we have:
 x = 1500
 y = 5000
 z = 3000
 
 ticket for seats in section a = 1500
 ticket for seats in section b = 5000
 ticket for seats in section c = 3000