methods:
calculator method:
insert number with as many decimals as possible
press equals sign
eg: 0.7 ˙ = 0.777777777… —> $$\frac{7}{9}$$
eg: 0.6˙3˙ = 0.636363636363… —> $$\frac{63}{99}$$
algebraic method
write out the stuffs eg: x = 0.166666666…
times by 10 eg: 10x = 1.666666666…
subtract these two thingys like so: $$\begin{align*} 10x &= 1.666666666\ldots \\ -\ x &= 0.166666666\ldots \\ \hline 9x &= 1.5 \end{align*} $$
then make x = 1 by doing: $$\frac{9x}{9}=\frac{1.5}{9}$$
you now have x= $$\frac{1.5}{9}$$
simplify to become $$\frac{1}{6}$$