Math question of the week (2)

Evan likes to play two games of chance, A and B.

For game A, the probability that Evan wins is 0.9. He plays game A seven times.

(a) Find the probability that he wins exactly four games. 

     For game B, the probability that Evan wins is p . He plays game B seven times.

(b) Write down an expression, in terms of p , for the probability that he wins exactly

     four games. 

(c) Hence, find the values of p such that the probability that he wins exactly four

     games is 0.15.