Verified answer

[tex]\Large\boxed{\begin{array}{l}\sf\dfrac{\diagdown\!\!\!\!\!\!12^2}{x}=\dfrac{\diagdown\!\!\!\!6^1}{9}\\\\\sf\dfrac{2}{x}=\dfrac{1}{9}\\\\\sf x=2\cdot9\\\\\huge\boxed{\boxed{\boxed{\boxed{\sf x=18}}}}\end{array}}[/tex]