A recipe requires 2 1/2 cups of flour 2 3/4 cups of sugar

Hi clciotola, you can do this kind of question with more work up front or less work up front. I'd do it with less work up front so let's go through that method:

Less work up front: Go through each item and see what the greatest number of cakes you can make with each. The lowest of these will be the right answer.

Flour: 15 cups, we need 2.5 cups each. Just keep going up the line to see how many cakes we can make: That means I can make 2 cakes with 5 cups, so 6 cakes overall with 15 cups. I've already got the answer narrowed to either A or B.

Sugar: 16 cups, we need 2.75 cups each. Same principle. I can make 2 cups with 5.5 cups, so to make 6 cakes I'd need 16.5 cups. I don't have that much sugar, so we're limited to 5 cakes. No need to even do milk because we're already at 5. Sugar will be the limiting factor.

You can also do this by figuring out which item will be the limiting factor. Since you have halfes, quarters and thirds, you'll need to put them on common bases by multiplying by 12. This will be ugly and I don't recommend it, although it will eventually work out to the same answer.

Hope this helps!
-Ron