Math problems are discounted at half price, and coupons are related to application problems. Can someone answer that?

This question does not explain whether coupons can be superimposed.

According to common sense, it can't be superimposed, so let's just say it can't be superimposed.

The first question is that your algorithm is correct.

448+448/2=672>500

You can use a coupon of over 500 MINUS 35.

672-35=637

The second question means that you can get a 15% discount if you buy two pieces at one time.

448×2×0.85=76 1.6>500

Similarly, 76 1.6-35=726.6.

You are also right about the third question.

448+9.9=457.9>300

Only coupons over 300 minus 15 can be used.

457.9- 15=442.9