\[\frac{18}{\sqrt{x - 4}} = 12\]
\[18 = 12\sqrt{x - 4}\]
\[2\sqrt{x - 4} = 3\]
\[4(x - 4) = 9\]
\[4x - 16 = 9\]
\[4x = 25\]
\[x = \frac{25}{4} = 6\frac{1}{4} = 6,25.\]