What I did on this is that I first work out of the outside squares of 10 x 10 square, then the ten squares
on the 4 sides of the square, I added them and take away the 4 corners because the 4 corners has doubled squares. There's also one thing that the numbers can be turned to letters and it's called algebra.
Here's the 2 ways of solving the grid:
1.) The first way of solving a grid is 10+9+9+8 = 36 by knowing it, we counted the squares all around the square, if you do it in mathematical way it would be like this n + n-1 + n-1 + n-2, the definition of the letter n is 10 but n isn't always 10, it can be any numbers than 10.
2.) Here's how we confirm that you can make the n any number, the second way solving it is, 9+9+9+9 = 36 or in mathematical way n-1 + n-1 + n-1 + n-1 = 36, you know that the definition of n is 10 but you can make n to any numbers than 10.
