I think you can answer this for yourself (but I will still tell you). Here �s how to figure these out:
Can you bake three cakes? Yes, so "cake" is countable.
"Cake" can also be uncountable, because you can talk about having "some cake" (which is different from "some cakes"). You can �t have "some fry" or "some idea" (although there is an expression "to have some idea", but that is a totally different situation).
Can you eat three fries? Yes, so "fries" is countable.
Can you have three ideas? Yes, so "idea" is countable.
I �m sure I gave you far too much information, but my basic answers are there, too. Yes, all three are countable.
Bruce ,