There are four parts of a circle, so you have to find out the area of the circle:-
10 cm=Radius
=100
=3.14
3.14*100=314

Now, find the area of the square box:-
Since half the side of the square is 10 cm, the total length of one side is 2*10 which is 20 cm.
Area=S*S
=20*20=400

Now subtract the area of the box from the area of the square:-
400-314= 86
That is the area of the shaded part.
Happy to help you!