Tickets fo a high school dance cost $0.50 each if purchased in advance of the dance,but are $0.75 each if bought at the door. ?
the continuation to the question is in the clarification
If you sold 100 tickets at the door, you’d have 100x$0.50 or $50. But you have $60. This is an extra $10. The extra comes from the cost at the door. You get $0.25 extra at the door. Four of these make a dollar, so you must have 4x10 to make $10. So you sold 40 at the door.