Question

I'VE BEEN STUCK IN THIS QUESTION FOR HOURS, HELP!

Answer 1

$\bf \textit{area of a sector of a circle}\\\\ A=\cfrac{\theta \pi r^2}{360}\quad \begin{cases} r=radius\\ \theta =angle\ in\\ \qquad degrees\\ ----------\\ r=21\\ \theta =90 \end{cases}\implies A=\cfrac{90\pi \cdot 21^2}{360}$