Answer
$29$
Work Step by Step
We have $\vec{AB}= \lt 7,3 \gt -\lt 0,0 \gt =\lt 7,3 \gt$
and $\vec{AC}=\lt 2,5 \gt -\lt 0,0 \gt =\lt 2,5 \gt$
$\vec{AB}\times\vec{AC}=\begin{vmatrix}\hat{i}&\hat{j}&\hat{k}\\7&3&0\\2&5&0\end{vmatrix}=0-0+(35-6)\hat{k}= 29\hat{k}$.
Therefore, $|\vec{AB}\times\vec{AC}|=\sqrt {(29)^2}=29$
