Given $\displaystyle u = 12$ $\displaystyle o = 3$ , what is the probability of P(X<9) ?
I have no clue how to do it...
Surely you're told the distribution! What is the context of the question? Is it a question from a problem set on normal distribution? Binomial distribution ....?
If you can't provide all the necessary background information to the question you're not going to get much help.