\( \sqrt{9-12 x}=9 \)
\( x = \frac{-72}{12} \)
Step 1 :\( (\sqrt{9-12 x})^2 = (9)^2 \)
Step 2 :\( 9-12 x = 81 \)
Step 3 :\( x = \frac{-72}{12} \)