A z-score can be defined as how many standard deviations away a value X from the mean. If a value is exactly an average, z-score will be 0. Values above the mean have positive z-scores whereas values below the mean have negative z-scores.
The Z score is computed as:
$$ Z = \frac{(X-\mu)}{\sigma} $$
Here μ is the Population mean and σ is the population standard deviation. X is called as raw score.Solution
$$ Z = \frac{(X-\mu)}{\sigma} $$