Is there something else to this question?
For example the numbers 45 and 20
There should be a dialogue question. Let's assume we gathered files and they were distributed with a mean of 45 minutes and a standard deviation of 12 minutes.
Now let's assume some random person had to wait less than 20minutes
Now to calculate the z-score we will use
[tex] \frac{45-20}{12} = 2.08 [/tex]
This gives us a z-score of 2.08