SOLUTION
ratio 6:18 will be broken to the lowest term.
Note that ratio means division. So this becomes
[tex]\begin{gathered} 6\colon8=\frac{6}{18} \\ 6\text{ will divide itself we have 1} \\ 18\text{ will divide 6, we have 3} \\ We\text{ have } \\ \frac{6}{18} \\ =\frac{1}{3} \end{gathered}[/tex]Hence the answer is
[tex]1\colon3[/tex]