Answer
$2.516516 =\frac{838}{333}$
Work Step by Step
$2.516516516516516$
$=2+\frac{516}{10^{3}}+\frac{516}{10^{6}}+...$
$=2 \Sigma^{\infty}_{n=1} 516(\frac{1}{10^{3}})^{n}$
$a=\frac{516}{10^{3}}$ and $r=\frac{1}{10^{3}}$
$2.516516516516516=2+\frac{\frac{516}{10^{3}}}{1-\frac{1}{10^{3}}}$
$=2+\frac{516}{999}$
$=\frac{2514}{999}$
$=\frac{838}{333}$