Explanation
to solve this we need to get the ratio, to do this get the same unit measure in both sides of the quotient
so
[tex]8\text{ in : 2 ft}[/tex]since
[tex]1\text{ ft=12 in}[/tex]replace,
[tex]\begin{gathered} 8\text{ in : 2 ft} \\ 8\text{ in : 2}(12\text{ in)} \\ 8\text{ in: 24 in} \\ \text{divide both sides by 8} \\ \frac{8\text{ in}}{8}=\frac{24\text{ in}}{8} \\ 1\text{ in:3 in} \end{gathered}[/tex]it means the scales factor is
[tex]1\colon3[/tex]