Which is cheaper for a 65$ item that costs $7 .25 to ship?
a 10% coupon off the cost of the item or free shipping?

I am going to say the cheapest would be 65$ would be the answer. Because if you want it to be shipped too you would add 7.25$ to 65$ to what you are paying for. And taking 10 dollars off (subtracting) you would get 62.25$ But if you would take 65$ from you buying it and used the coupon you would have to pay 55$ The cheapest way is to buy that item (the item costs 65$) and use the 10% off coupon.

Its a right angled triangle not a right triangle