You can
put this solution on YOUR website!Let the original side length be called x..
the original area is equal to

The new side length is (x-2)
The new area is (x-2)^2
the change in area is the original area - the new area:

so the originale sqares dimensions where 4cm by 4 cm.
I hope this helps
P.S. I am trying to start up my own homework help website. I would be extremely grateful if you would e-mail me some feedback on the help you received to adam.chapman@student.manchester.ac.uk