Answer :
[tex]\bf \textit{area of a sphere}\\\\ SA=4\pi r^2~~ \begin{cases} r=radius\\ \cline{1-1} SA=64\pi \end{cases}\implies 64\pi =4\pi r^2 \\\\\\ \cfrac{64\pi }{4\pi }=r^2\implies 16=r^2\implies \sqrt{16}=r\implies 4=r[/tex]
[tex]\bf \textit{area of a sphere}\\\\ SA=4\pi r^2~~ \begin{cases} r=radius\\ \cline{1-1} SA=64\pi \end{cases}\implies 64\pi =4\pi r^2 \\\\\\ \cfrac{64\pi }{4\pi }=r^2\implies 16=r^2\implies \sqrt{16}=r\implies 4=r[/tex]