Actually Welcome to the concept of Areas and Volumes.
Area of Shaded region = Area of Square - Area of inscribed Circle.
Radius if circle = 10/2 ==> 5 units
hence,
Area of circle = 25 π units
Area of square = (10)^2 ==> 100 units
hence the area of shaded region = 100 - 25π
==> Area of shaded region = 25 (4 - π)
Correct option is G.)