Answer:
For many(n) tickets, the average payoff is 0.5n, in which n is the number of tickets.
Step-by-step explanation:
1/1000 chance of winning.
This means that there is an 1/1000 probability of you earning $500.
1 - 1/1000 = 999/1000 chance of losing.
In this case, you earn nothing.
What is your average payoff from many tickets

Your average payoff from a ticket is 0.5. So for many(n) tickets, the average payoff is 0.5n, in which n is the number of tickets.