When the distribution is negatively skewed, how do you find the probability that a sample would be less than ___?

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I think my question has a really simple answer, but I’d still really appreciate your help :)

I’m given that a distribution is negatively skewed with a mean of 55 and a variance of 15, and then am asked: for a random sample of n=80, what is the probability that X is less than 54 and X is between 54 and 58.

I know how to go about this if it was normally distributed which would be to find the expected value of m and then the z-score. I’m wondering if that would be the same for a distribution that is negatively skewed.

Thank you!