Hey mathplease.

Hint: P(X >= 9) = P(X = 9) + P(X = 10) = (1/2)^10 + 10*(1/2)^10 = 1/1024 + 10/1024 = 11/1024.

Remember that in probability, the aim is to use the probability axioms. When you get used to the axioms (and when they become your intuition) then probability will get a lot easier.