Question 853192
If you use the coupon first,
(P-7)*.80 (the reciprocal of .20)
If you use the discount first,
.8P - 7
.
Let's assume the pizza is $20.
Coupon first: (20-7)*.8 = $10.40
Discount first: (.8*20)-7 = $9.00
.
You'll pay $1.40 more by using the coupon first.