[tex]\bf \textit{circumference of a circle}\\\\ C=2\pi r~~ \begin{cases} r=radius\\[-0.5em] \hrulefill\\ C=21.98 \end{cases}\implies 21.98=2\pi r\implies \cfrac{21.98}{2\pi }=\boxed{r} \\\\[-0.35em] ~\dotfill\\\\ \textit{area of a circle}\\\\ A=\pi r^2\qquad \qquad A=\pi \left( \boxed{\cfrac{21.98}{2\pi }} \right)^2\implies A=\cfrac{21.98^2}{2^2\pi }\implies A\approx 38.445[/tex]
