A fair coin is flipped 50 times,
a. What is the probability of the event that exactly three heads come? b. What is the probability of the event that 20 tails come? c. What is the probability of the event that exact 15 heads and 35 tails come? d. What is the probability of the event that more heads come than tails? e. If the first 10 flips result in all tails then what is the probability of the event that total 25 heads come?
a) $2^{50}$ possible outcomes. $50 \choose 3$ correct ones
$$\frac{50 \choose 3 }{2^{50}}$$
The other ones are similar, try to find them yourself, so you get to learn something.