Hey Matt1993.

Hint: For discrete distributions P(X <= x) = Sigma (i = 0 to x) P(X = x) [Assuming that the first event is X = 0]. For continuous distributions, P(X < x) = Integral [-infinity,x] f(u)du. These are standard definitions.

Given the above, what is P(X = x) for (a) and (c) and what is f(u) for b?