3. Solve (if possible) each of the following system of three equations in three variables using the method of Gauss-Jordan elimination. (20%)

\( \begin{cases} x_1 + 2x_2 - x_3 = 3 \\ 2x_1 + 4x_2 - 2x_3 = 6 \\ 3x_1 + 6x_2 + 2x_3 = -1 \end{cases} \)