What is the related addition fact for 5 + 6

Which expression gives you the distance between the points (5,1)and(9,-6)

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?

Need plz been trying to do it for a long time and still haven’t succeeded