Tim puts some extra money in his box before he began. Assuming all tickets are the same price, write an equation that represents the situation in the table. Explain how to use your equation to determine the amount of money originally in the before any tickets were sold and the price of each ticket.

number of tickets sold        total money in box (dollars)
7                                                  108.75
13                                                 146.25
18                                                   177.50