Answer
$x=0$ or $x=-9$.
Work Step by Step
We know that for a matrix
\[
\left[\begin{array}{rrr}
a & b & c \\
d &e & f \\
g &h & i \\
\end{array} \right]
\]
the determinant, $D=a(ei-fh)-b(di-fg)+c(dh-eg).$
Hence here $D=x(x\cdot(-2)-0\cdot1)-2(1\cdot(-2)-0\cdot6)+3(1\cdot1-x\cdot6)=0\\x(-2x)-2(-2)+3(1-6x)=7\\-2x^2+4+3-18x=7\\2x^2+18x=0\\2x(x+9)=0.$
Hence by the zero product property $x=0$ or $x+9=0\\x=-9$.
