help with SAT math please

jason buys and sells baseball cards to earn extra amoney. he purchased the card of a player who performed so well throughtout the year that jason was able to mark the card up 20% more than what he orginally paid. when he sold the card, he gave one of his good friends a discount of 10% off his already marked up price. what was Jason's percent profit on the card?

Question

help with SAT math please 

jason buys and sells baseball cards to earn extra amoney. he purchased the card of a player who performed so well throughtout the year that jason was able to mark the card up 20% more than what he orginally paid. when he sold the card, he gave one of his good friends a discount of 10% off his  already marked up price. what was Jason's percent profit on the card?

anonymous · Answer

let Jason's buying price be 100
20% markup = 20% of 100 = 20
so selling price/marked price = 120
discount if 10% on marked price
discount = 10% 0f 120 = 12
so final selling price is 120 - 12 = 108
so profit = 108-100 = 8

profit percent = 8/100 * 100% = 8%