a. On Thursday, 25 tickets were sold in total, that means you sold 15/25. this is simplified to 3/5, which equals 60%.
b. On Friday, you sold 9/25 tickets. If you multiply both 9 and 25 by 4, you get 36/100, or 36%.
c. In total, 50 tickets were sold between the two days. You sold 24 (9+15) of them. 24/50 equals 48%