Hello! Remember you have to write complete questions in order to get good and exact answers. Here you haven't provided any diagram so I'll assume we are talking about a square. If so, then the area of the square is given by:
[tex]A=s^2 \\ \\ s:Side \ of \ the \ square[/tex]
From the figure below, we know that the side of the square is:
[tex]s=20m[/tex]
So the area can be found as:
[tex]A=(\sqrt{40})^2 \\ \\ A=40m^2[/tex]
Finally:
The shaded region has an area of 40 square meters