Good Morning!
Well, i believe here in this very case, and independent variable stands for itself, while a dependent variable, well, it depends on others. So in this case, Independent variables must be the amount of cans you buy of cat food. The dependent variable, well that must be the cost. Depending on how many cans you buy, the cost changes! :)
If you need any more help, tag me, and happy Studying!
Thank you,
Darian D.
(almost forgot how to spell my name!)