What is the value of x?

Erin bought christmas cards for $2 each to send to her family and friends. which variable is the dependent variable?

Sam is picking fruit from a basket that contains many different kinds of fruit. which set of events is independent?

Let x have probability generating function gx (s) and let un generating function u(s) of the sequence uo, u1, satisfies p(x > n). show that the (1- s)u(s) = 1 - gx(s), whenever the series defining these generating functions converge.