[tex] \bf \textit{circumference of a circle}\\\\
C=2\pi r~~
\begin{cases}
r=radius\\[-0.5em]
\hrulefill\\
C=87.92
\end{cases}\implies 87.92=2\pi r\implies \cfrac{87.92}{2\pi }=\boxed{r}
\\\\[-0.35em]
~\dotfill\\\\
\textit{area of a circle}\\\\
A=\pi r^2~\hspace{7em}A=\pi \left( \boxed{\frac{87.92}{2\pi }} \right)^2
\\\\\\
A=\pi \cdot \cfrac{87.92^2}{4\pi^2}\implies A=\cfrac{87.92^2}{4\pi }\implies A\approx 615.127998 [/tex]
