Write a system of equations to represent the problem: Tickets to a movie cost $4 for children, $5 for senior citizens, and $7 for adults. O the opening weekend of the new Avengers movie there were 2,400 tickets sold at one theater. There were $14,700 in ticket sales. There were also twice as many senior citizens as there were children. x+y+z = 2,400 4x+5y+7z=14,700 O 2x-y=0 x+y+z 14,700 4x+5y+7z=2,400 2x+y=0 x+y+z = 2,400 4x+5y+7z 14,700 x=2y x+y+z=14,700 4x+5y+7z 2,400 - x+2y+z=0