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Here is the problem: A score of 85 comes from a distribution with mean 70 and standard deviation 10. Find its z-score.

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Z-score from x, mean and SD.

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Subtract the mean from the value.

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Divide by the standard deviation.

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Look up the area to the left (percentile).

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So the answer is z equals 1.5 (percentile approximately 93.32 percent).

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85 lies 1.5 standard deviations above the mean; about 93.32 percent of a normal population lies below it.

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Reverse: μ plus zσ equals 70 plus (1.5)(10) equals 85.