>>52824534this is how I did it.
the lower total is the cost of the food and drink, and the higher total is the the total spent on food and drink plus service, which is the tip.
so you take the lower total, which is what your tip is based off and compare that to the actual tip. multiply each tip by 10, as you are assuming they tipped 10% or more as stated in the question. In order for that to be true, the tip must be equal to or exceed the total of food and drink bought.