A$0$
a
(a) $D = \left| {\,\begin{array}{*{20}{c}}0&1&{ - 1}\\{ - 1\,\,\,}&0&{\,\,\,2}\\1&{ - 2\,\,\,}&{\,\,\,0}\end{array}\,} \right|\, = \,0$
$D = \left| {\,\begin{array}{*{20}{c}}
1&1&{ - 1}\\
{ - 2\,\,\,}&0&{\,\,\,2}\\
3&{ - 2\,\,\,}&{\,\,\,0}
\end{array}\,} \right|\, = \,14 \Rightarrow {D_1} \ne 0$
$D = 0$ and ${D_1} \ne 0$,hence the system is inconsistent, so it has no solution.