\[\mathbf{\ }3x^{2} = 18x\]
\[3x^{2} - 18x = 0\]
\[3x(x - 6) = 0\]
\[x = 0\ \ \ \ \ \ \ \ \ \ x - 6 = 0\ \ \ \ \]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = 6\]
\[Ответ:\ \ \ \ \ x = 0\ \ \ и\ \ \ x = 6.\]