M = \(\begin{bmatrix}3 & 4 & 6\\2 & 1 & -1\\-1 & 3 & 5\end{bmatrix}\) |M| = 3\(\begin{bmatrix}1 & -1\\3 & 5\end{bmatrix}\) - 4\(\begin{bmatrix}2 & -1\\-1 & 5\end{bmatrix}\) + 6\(\begin{bmatrix}2 & 1\\-1 & 3\end{bmatrix}\) 3(5 + 3) - 4(10 - 1) + 6(6 + 1) = 24 - 36 + 42 = 30