I really need help on how to do the variance for this.

I know how to work out variance from a set of data and stuff, but the wording of this question is really confusing me. Could you please show all your steps so that I understand. Also I have changed one of the values so it is NOT the same as my homework, because I want to do that myself.... I just need someone to explain/show the steps. Thank you

Here are 10 values of a variable x. Find the variance using the coded values, u = x-20.

18.9 20.7 19.3 20.1 21.3 19.6 20.5 20.9 18.8 20.8

Thanks again