Probability

. Six pennies are flipped. What is the probability of getting
a. two heads and four tails?
b. at least three heads?
c. at most two tails?

2. A bag contains one red marble and one white marble. Marbles
are drawn and replaced in a bag before the next draw.

a. What is the probability that a red marble will be drawn two
times in a row?
b. In ten draws, what is the probability that a red marble will
be drawn at least five times.

What's your answer?
And if u solve this without combinatorics,please post your solution...