Answer
4104
Work Step by Step
We are given:
$A=\begin{bmatrix}
1 & 2 & -1\\
2& 1 & 4
\end{bmatrix}$
$C=\begin{bmatrix}
1 & 0 & 5\\
3& -1 & 4\\
2 & -2 & 6
\end{bmatrix}$
$\rightarrow AC=\begin{bmatrix}
5 & 0 & 7\\
13& -9 & 38
\end{bmatrix} $
$B=\begin{bmatrix}
2 & 1\\
5& -2\\
4 & 7
\end{bmatrix}$
$\rightarrow (AC)B=\begin{bmatrix}
38 & 54\\
133 & 297
\end{bmatrix}$
Hence here:
$\det(ACB)=38.297-54.133=4104$
