help

Notice that $\begin{bmatrix} a&d&g\\b&e&h\\c&f&i \end{bmatrix} = \begin{bmatrix} a&b&c\\ d&e&f\\ g&h&i \end{bmatrix}^{\mathbf{T}}$

So their determinants are the same.

$\begin{vmatrix} a & d & g \\ b & e & h \\ c & f & i \end{vmatrix} = \begin{vmatrix} a&b&c\\d&e&f\\g&h&i\end{vmatrix} = -24$