Whats an equation that make x=31 ? like in other words give me an equation where it leads down to 31

How to do this , and can some one explain

How far could you drive on 50 gallons of gas

The total ticket sales for a high school basketball game were $2,260. the ticket price for students were $2.25 less than the adult ticket price. the number of adult tickets sold was 230, and the number of student tickets sold was 180. what was the price of an adult ticket?