Area of the square with side 20:

$\text{Area of square} = 20^2 = 400$

The inscribed circle has diameter 20, so radius $= 10$:

$\text{Area of circle} = \pi(10)^2 = 100\pi \approx 314.16$

Area of the shaded region:

$400 - 314.16 \approx 86$