The question is at this link: Imageshack - 50492509.png
I recommend zooming in on the image because it's a little fuzzy.
Addition and subtraction of matrices is possible if they are of the same dimensions. If A is a matrix, then B should also be a matrix if they are to be added or subtracted. And the resulting matrix is also of the same dimension. Use this concept to find out whether addition or subtraction is possible in those cases or not!
So for i), W must be the same size as Z, right? So stating the order of w for this question would be 3x3? What is I3?
You should find notation such as (and for that matter ) in your class notes or textbook .... Have you gone back and reviewed this material? (I'd be surprised if what was said in post #2 was not also in your classnotes ....)