Maria needs to buy shoes for $50, jeans for $40, and a shirt for $20. she has a coupon that gives her a discount of x percent on shoes. she has a second coupon that gives her a discount of y percent on jeans. the third coupon gives her a discount of z percent on her total purchase. she cannot combine the coupon for the total purchase with the other two coupons. these expressions give both possibilities for the total cost of maria's purchase after the coupons are applied, the variables represent the percentages as decimals.