Answer
$x=-11$
Work Step by Step
We know that for a matrix
\[
\left[\begin{array}{rr}
a & b \\
c &d \\
\end{array} \right]
\]
the determinant, $D=ad-bc.$
Hence here $D=-2\cdot6-4x=-12-4x.$
$-12-4x=32\\-4x=44\\x=-11$