Answer
9
Work Step by Step
$\textbf{u}\times\textbf{v}=\begin{vmatrix}\hat{i}&\hat{j}&\hat{k}\\2&-1&0\\0&2&1\end{vmatrix}=-\hat{i}-2\hat{j}+4\hat{k}$
$(\textbf{u}\times\textbf{v})\cdot\textbf{w}=(-\hat{i}-2\hat{j}+4\hat{k})\cdot(3\hat{i}+\hat{j}-\hat{k})$$=-3-2-4=-9$
The volume of the parallelepiped= $|(\textbf{u}\times\textbf{v})\cdot\textbf{w}|= 9$
