Answer
$9$
Work Step by Step
Volume of a parallelepiped is defined as:
$V=|a \cdot (b \times c)|$
$b \times c= \lt -1,1,2 \gt \times \lt 2,1,4 \gt=\lt 2,8,-3 \gt$
$|a \cdot (b \times c)|= |\lt 1,2,3 \gt \cdot \lt 2,8,-3 \gt |$
$=|1 \cdot2+2 \cdot 8+ 3 \cdot (-3)|$
$=|2+16+(-9)|$
$=9$
