Solution
= Solution
Subtract the first vertex from the remaining three to obtain edge vectors $a=(1,2,-2)$, $b=(0,1,3)$, $c=(-1,-1,0)$. Their <scalar triple product> is
$$
a\cdot(b\times c)=(1,2,-2)\cdot(3,-3,1)=-5.
$$
A <tetrahedron> occupies one sixth of the corresponding <parallelepiped>, so its <volume> is
$$
\boxed{V=\frac16|a\cdot(b\times c)|=\frac56.}
$$
The absolute value removes the orientation sign of the <determinant>.