hi barandaman

here's the LHS using Latex.

I think you need to do two things.

(i) tell us what the question asks

(ii) show how you got this far.

Please use Latex:

You start with square brackets math and end with square brackets /math

The code for the above is:

There is a code for the line over the y but I forget at the moment. But ybar is clear I think.

Bob