Mary is not intelligent enough to do this test.

Do the test carefully. We have enough time.

You have to work hard enough if you want to pass your exams. (Note: The sentence is fine as is, but this rephrasing adds emphasis.)

They can't live in this house because it is not big enough.

My desk has too much money. (If you meant "enough," it should be rephrased as: "My desk has enough money.")

This store has a lot of snacks, but I don't have enough money. (Correct as is.)