56
that’s the answer because -500 is your starting number, however many tickets you sell is multiplied by 10 to show your profit, however for every ticket you have to add -1 to the equation. 55 would be 550 but the negative would be 555, however with 56 you have 560 and the negative is only 556, so you have a 4 dollar profit.
I’m not the best at explaining things but I hope this helped.