Use a coupon worth
$20 off your entire purchase
20% off your entire purchase?
Whichever option you choose, justify your reasoning with mathematics.
As a follow-up to this, there could be a conversation around when it would be worth it to take the 20% coupon. What if it was a 30% coupon? Where is the breaking point?
To extend this even further as a full lesson around percent markup and discount, Dan has done some extensive work on the lesson design.