[tex] \frac{A_{\triangle1}}{A_{\triangle2}} = \frac{4}{7} \Longrightarrow 4A_{\triangle2}=7A_{\triangle1} \\
A_{\triangle2}-A_{\triangle1}=36~cm^2 \Longrightarrow A_{\triangle2}=A_{\triangle1}+36 \\
Replace: \\
4(A_{\triangle1}+36)=7A_{\triangle1} \\
4A_{\triangle1}+144=7A_{\triangle1} \\
3A_{\triangle1}=144 \\
\boxed{A_{\triangle1}=48~cm^2} \\
A_{\triangle2}=48+36 \\
\boxed{A_{\triangle2}=84~cm^2}[/tex]
