He can buy 20, because half of 100 is 50 since he wants to leave with at least 50 dollars, then you divide 2.50 from 50 and the answer is 20 tickets that he can buy
100 - 50 = 50 50/2.50 = 20 Subtract 50 from the original $100 to find out the most he can spend and still have $50 left. This amount $50 is then divided by the price of each raffle ticket $2.50, and he can buy 20 tickets.
