Answer
$-6$.
Work Step by Step
If $A$ and $B$ are $n\times n$ matrices, then $det(AB)=det(A)det(B)$. Also $det(A^T)=det(A)$ and if $det(A)\ne0$, then $det(A^{-1})=\frac{1}{det(A)}$
Hence here $det(AB)=det(A)det(B)=-2\cdot3=-6$.
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