so Mary went over with 100 bucks, she spent 22.65 and then 33.31, so she has pay for 22.65 + 33.31 = 55.96, but low and behold, she has a coupon off her total purchase, so she only will have to pay for 55.96 - 10 = 45.96.
she goes over to the counter, hands the $100, 100 - 45.96 = 54.04 <- change.