[tex]\textit{circumference of a circle}\\\\ C=2\pi r~~ \begin{cases} r=radius\\[-0.5em] \hrulefill\\ C=51 \end{cases}\implies 51=2\pi r\implies \boxed{\cfrac{51}{2\pi }=r} \\\\[-0.35em] ~\dotfill\\\\ \textit{area of a circle}\\\\ A=\pi r^2\qquad \implies A=\pi \left( \cfrac{51}{2\pi } \right)^2\implies A=\cfrac{51^2}{2^2\pi }\implies A\approx 206.98[/tex]
