4. Two baseball teams which are evenly matched play a series of games in which the first team to win four games is declared the winner of the series. What is the probability that they will have to play seven games before the series is decided, assuming that each team has a 50-50 change of winning the each game? Express your answer as a common fraction.
16. Ian uses a weighed coin to decide whether to move north or east. If the coin comes up head, he moves north and if the coin comes up tails, he moves east. Ian discovers after many random walks that he is sixteen times more likely to end up 3 blocks north and 1 block east than he is to end up 1 block north and 3 block east after 4 coin tosses. What is the probability that the coin show up heads? Put you answer as a common fraction.
I am terrible at probability. Please help!