Assuming that the triangles shown in the picture are similar triangles, then the ratios of corresponding sides are the same. Then:
[tex]\begin{gathered} \frac{x}{9}=\frac{2}{4} \\ \Rightarrow x=\frac{2}{4}\times9 \\ \Rightarrow x=\frac{9}{2} \\ \Rightarrow x=4.5 \\ \Rightarrow x=4+\frac{1}{2} \\ \Rightarrow x=4\frac{1}{2} \end{gathered}[/tex]Therefore, the value of x is:
[tex]4\frac{1}{2}[/tex]