A12-pounded bag of dog food costs $12.36. a 15-pounded bag of cat food cost $15.30. which is a better

The 15 pound of cat food because if you divide 15.30 by 15 it gives you 1.02 which is the price per pound.
For the dog food you would divide 12.36 by 12 to get 1.3.
The price per pound for the cat food is cheeper the the dog food which means you get more food at a lower cost.

Hope this helps!