\[x^{2} - 3x - 12 + 12 = 0\]
\[x^{2} - 3x = 0\]
\[x(x - 3) = 0\]
\[x = 0;\ \ \ \ x = 3.\]
\[\left\{ \begin{matrix} x = 0 \\ y = 4 \\ \end{matrix} \right.\ \ \ \ \ \ или\ \ \ \ \left\{ \begin{matrix} x = 3 \\ y = 7 \\ \end{matrix} \right.\ \]
\[Проверка:\]
\[Ответ:(0;4)\ и\ (3;7).\]