I am stuck and I need help

TRY THESE PROBLEMS (Set !1) 11. A retailer bought towels for $84 a dozen for a special sale. Although her regular markup is 40% of selling price, for this special sale she will be using 30% of selling price. What percent markup on cost does the sale price represent? 12. A retailer needs to sell a new series of baseball cards at $2 each. He finds a supplier who will charge him $15,a dozen. Should he buy these if he must add 55% of selling price as his markup? 13. A travel kit is to retail for $25.30 after a markup of 15% on cost. Find the percent markup on selling price. 14. A wallet that cost $7.80 to produce is sold to a retailer for $1 1.00. The retailer sells it at $17.50. Find: a. The producer's percent markup on cost; b. The retailer's percent markup on selling price