Explanation:
I assume "fair game" means that there is no profit and the expenses are equal to the income or sales.
we have clear expenses :
1× $100
3× $20
that is in total : $160
now we need to make sure that we generate exactly $160 by selling the tickets.
we have 100 tickets that should lead to $160.
how much should 1 ticket cost ?
well, 160/100 = $1.60