I'm assuming a quarter-circle is exactly 1/4 of a circle. Thus if you have 4 congruent quarter-circles, that should mean they make a complete circle.
If that is the case, then we can find the area of the full circle using pi*r^2.
So the area of the circle is 5^2*pi or 25pi.
To find the area of the shaded region, we subtract the area of the circle from the area of the square.
The area of the square is 10^2 or 100.
So the area of the shaded region is 100 - 25pi.
My calculator says that equals roughly 21.46
