Solution
= Solution
The <cross product> of the two in-plane directions is $\mathbf u\times\mathbf v=(-5,1,2)$, with <Euclidean norm> $\sqrt{30}$. Either sign gives a <unit normal vector>:
$$
\boxed{\hat{\mathbf n}=\pm\frac{(-5,1,2)}{\sqrt{30}}}.
$$
The <plane> equation is $\hat{\mathbf n}\cdot(\mathbf r-\mathbf A)=0$, so the <distance from a point to a plane> gives
$$
\boxed{p=|\hat{\mathbf n}\cdot\mathbf A|=\frac2{\sqrt{30}}}.
$$