Answer
$(15-0.5r)$ dollars
Work Step by Step
The total cost of the tickets is equal to the product of the number of tickets bought and the cost per ticket.
Thus, $r$ raffle tickets would cost a total of $r(0.50) = 0.5r$ dollars.
The remaining money can be found by deducting the cost of the tickets from $\$15$.
Thus, the amount of money left is:
$$(15-0.5r)\text{ dollars}$$
