An excellent free throw shooter attempts several free throws until she misses.

a) If p=0.9 is her probability of making a free throw, what is the probability of having the first miss on the 13th attempt or later?

b) If she continues shooting until she misses three, what is the probability that the third miss occurs on the 30th attempt?

Thank you so much in advance for your help... I thought calculus based statistics would make more sense to me.