What's the probability of an unfair coin? 3 8's. And you could convert that to a decimal or a percentage or whatever you'd like. Now, given that I have picked a fair coin, what is the probability that I will get heads twice? So let me write it this way. And this is just notation right here. So the probability of, I'll call it heads, heads, so I get two heads in a row, given that I have a fair coin.