Area of figure created by geomitrical shapes

Radius of the circle = $10$ cm

Side of the square = $20$ cm. ( $10 \times 2)$

$\therefore$ Area of square = $20 \times 20 = 400$ sq.cm

Area of the circle = $\pi \times r^2$ $= 3.14 \times 100 = 314$ sq.cm

Area of square - Area of circle = $400 - 314$

$= 86$ sq.cm . This is the area of the $4$ leftover parts and the area of the $4$ parts is equal.

$\therefore$ Area of the shaded part = $\dfrac{86}{2} = 43$ sq.cm

(Upvote if you are satisfied)

Area of the shaded portion is area of the square minus the area of the circle, then divide the result by two. We have

$A=\dfrac{20^2-(3.14)(10^2)}{2}=$ $\color{#D61F06}\boxed{43}$