Answer:
Purchases greater than 66.67 dollars should use coupon 2, while purchases between 20 dollars and 66.67 should use coupon 1.
Step-by-step explanation:
Coupon 1 must be used as long as those 10 dollars represent more money than 15% of coupon 2.
For example, if the purchase is the minimum of $ 20, 10 dollars represents half of the purchase, therefore in this case it is better to use coupon 1.
In this case, coupon 2 would only be a discount of 3 dollars (20 * 0.15).
So when from what value would it be better to use coupon 2, it would have to be calculated when it is worth more than 10 dollars.
10 = x * 0.15
x = 10 / 0.15
x = 66.67
That is to say that from the purchases greater than 66.67 dollars, coupon 2 would have a discount equivalent to 10 dollars or more.
