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 upper balcony tickets. the theater sold $37,500 in tickets for that performance. the money made from mezzanine tickets alone was 4 times the money made from upper balcony tickets. how many lower level tickets were sold for that performance?