If someone were to say, what's the probability of you pick the unfair coin and then get two heads in a row with that unfair coin, you would get this number. Now if someone were to say, either way, what's the probability of getting two heads in a row? Because that's what they're asking us here. What is the probability of getting two heads? So we could get it through this method, by chance picking the fair coin, or through this method, by chance picking the unfair coin. So since we can do it either way, we can sum up the probabilities. Either of these events meet our constraints.