Solution
= Solution
The plane contains $(1,0,1)$ and has <normal vector> $(0,1,2)$, so its equation is $y+2z=2$. In the equation $\mathbf n\cdot\mathbf r=d$ with a <unit normal>, $|d|$ is the perpendicular distance from the origin. Consequently
$$
\boxed{\text{distance}=\frac2{\sqrt5}.}
$$