Given the information, we have the following triangles:
since they are similar, we can write the following proportions:
[tex]\frac{9}{6}=\frac{s}{4}[/tex]solving for s we get the following:
[tex]\begin{gathered} \frac{s}{4}=\frac{9}{6} \\ \Rightarrow s=\frac{9}{6}\cdot4=\frac{36}{6}=6 \\ s=6 \end{gathered}[/tex]therefore, the measure of the shortest side is 6