7,10) and (7,20). Slope or no slope

Sara sells beaded necklaces she makes a profit of 4 dollars pn every neclace she sells which table represents the profit sara makes

Melanie is buying a bathing suit that costs 39.99. she is given a discount at the cash register of $6.00 when she scratched 15% off on a game piece for a store promotion. what will the sale price of melanie’s bathing suit be?

Rewrite so the subject can be y in the formula d=m-y/y+n