Answer: 36 cm
Step-by-step explanation:
Since, [tex]\triangle ABC\sim \triangle XYZ[/tex]
In the similar triangles the corresponding sides are in the same proportion,
[tex]\implies \frac{AB}{BC} = \frac{XY}{YZ}[/tex]
[tex]\implies \frac{6}{18} = \frac{12}{YZ}[/tex]
[tex]\implies 6YZ =18\times 12[/tex]
[tex]\implies 6YZ =216[/tex]
[tex]\implies YZ=36\text{ cm}[/tex]