A theater is showing a ballet performance. Tickets are available on three levels in the performance hall. Lower level tickets cost $35, mezzanine tickets cost $25, and upper balcony tickets cost $15. For a certain performance the theater sold 5 times as many lower level tickets as balcony tickets. The theater sold $37,500 in tickets that performance. The money made from mezzanine tickets alone was 4 times the money made from balcony tickets. How many of lower level tickets where sold for that performance?