Mary paid 1.97 for toothpaste and a bar of soap using a discount coupon if the toothpaste cost 1.29

Mary paid 1.97 for toothpaste and a bar of soap using a discount coupon if the toothpaste cost 1.29 and the song cost 83 cents. What is the value of the discount coupon?

Find the full price package:
1.29 + 0.83 = 2.12

The value of the discount coupon is the money off, so:
2.12 - 1.97 = 0.15