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