[tex]\bf \textit{circumference of a circle}\\\\
C=2\pi r\quad
\begin{cases}
r=radius\\
------\\
C=12\frac{1}{4}\pi \\\\
\qquad \frac{12\cdot 4+1}{4}\pi \\\\
\qquad \frac{49}{4}\pi
\end{cases}\implies \cfrac{49\pi }{4}=2\pi r
\\\\\\
\cfrac{49\underline{\pi} }{8\underline{\pi} }=r\implies \cfrac{49}{8}=r\implies 6\frac{1}{8}=r[/tex]
