To find area, you multiply length * width. There are 4 sides on a number, so we need to have a equation like this. x * x * y * y = 12cm. If we do 4 * 4, we get 8. We could also use 2 * 2 = 4. 8 + 4 = 12. So, width = 8, and length = 4.
Hope this helps! ☺♥