Do you know what the mole ratio means?

It's something telling you how many moles of such reagent/product is involved when a certain number of moles of reagent/product is used/obtained.

From your equation (which by the way could be written much better than this), you see that 2 moles of C4H10 react with 13 moles of O2.

So, the mole ratio is 2:13