Easy

1. Two coins, one is double tail, you see one
   1. three pancakes: golden-golden, golden-brunt, brunt-brunt, see one golden, probability that the other side is golden two
2. Two coins - one toss n+1, one toss n, probability that n+1 gets more tail than n man?

Medium

1. Use coins to create probabilities
   1. fair coin to create 1/3 probability - toss twice, one result is retoss
   2. unfair coin to create 1/3 probability - combine two toss as one

Hard