What is the slope of the line between -8,5 and 4, -3

Henrik is shopping at a store. the store is having a sale on all items. henrik also has a coupon for an additional amount off the sale price. the expression 0.7p – 15 represents the final price, in dollars, of items with a regular price of p dollars. complete the table by filling in the value of the coupon and the percent discount of the store's sale.