number of variables as long as you consistently put them everywhere so you can always add more conditioning and so often that's the version we'll be using this will have many things we've already observed in the past we want to conditioned on and then we'll want to apply the equation the left law of total probability and we'll just carry along everything so do our math as if it doesn't exist we just need to consistently carry it along very straightforward got to be careful you can't drop it anywhere same thing is