Answer:
Triangle small ABC
Triangle big DEF
AB = 8 cm , BC = 12 cm , DE = 20 cm , EF = x
So;
[tex] \frac{AB}{DE} = \frac{BC}{EF} \\ \\ \frac{8}{20} = \frac{12}{x} \\ \\ 8x = 12 \times 20 \\ 8x = 240 \\ \\ x = \frac{240}{8} \\ \\ x = 30 cm[/tex]
I hope I helped you^_^
