Oops, I didn't think that through. You can't write a proper chemical equation without a formula. Heh. It's late, over here. Anyway, you've done a good job guessing a formula. Now, you've got grams of carbon dioxide and water. How many moles of each is that? The carbon and hydrogen come from menthol, so can you figure out what multiples of carbon and hydrogen you need? The balance is oxygen, but that you'll figure out later.