The ratio of their perimeters is the same ratio between corresponding sides.
Looking at the image, the side ST corresponds to the side BC.
Calculating their ratio, we have:
[tex]\begin{gathered} \text{ratio}=\frac{ST}{BC} \\ \text{ratio}=\frac{12}{8} \\ \text{ratio}=\frac{3}{2} \end{gathered}[/tex]
So the ratio of their perimeters is 3 : 2
