Answer: All real numbers :)
Find the ticket unit cost: divide the total paid, $324, by the number of tickets, x. Then the form of the unit cost is
$324
--------- .
x
This question is highly unusual in that you write "x" as the number of tickets sold, instead of a specific number of tickets. Supposing that you'd sold 100 tickets for $324, then the unit cost would be, much more typically, a numeric ratio:
$324
----------------- = $3.24/ticket
100 tickets
This would be 11.83 I hope you pass your test/quiz :)