probability calculation

Yes, provide much more information. For example is "X-50" representing X minus 50 or a range, so X:50. Also, hey what in the world were you provided. Obviously your instructor did not just provide the following and expect you to be able to answer it, so why do you think we divine such omnipotent powers?

Calculate the probability that P [X-50]> 0
(formalize the question and continue with the resolution).
But is data provided? X could be any type of data (continuous, binary presented as percentages), I would have to imagine more information should be available or at least tell us the context. Is this suppose to be a one-sided one-sample ttest and they want a p-value, which is not the probability that P[X-50] > 0. I am gonna have to give up on trying to help unless you provide drastically more information.

@Dason - isn't P vs Pr used for continuous vs discrete or vice versa?