2z - 31 = -9z + 24 can anyone tell me how to know if we must subtract or add? like we must write it as this when we solve it 2z - (- 9z) or 2z + -9z

Someone answer asap for ! 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?