The wording confuses me. How can this question be done?

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Q: The time taken by a bus to travel between Town A and Town B can be modeled by a normal distribution with Mean minutes and Standard Deviation . A passenger on the bus needs to be in Town B minutes after the bus leaves Town A. Find the value of such that there is only a chance the passenger does not arrive in time.

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I understand standardizing should be done but not aware how it should be done? The answer is .