Me this looks easy but i don’t understand it tho

Which expression is equivalent to sq-80

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.

The blue lake trail is 11 1/2 miles long. grace has hiked 1 1/2 for 2 hours. how far did she from the end of the trail