Normally my teacher would tell me to do $\vec{AB}$ x $\vec{AC}$ which have the same initial point and the cross product of that would be the line/vector perpendicular to the plane or perpendicular to those 2 vectors.
But in this question, we have different initial point. What does this mean and how can i visualise this? Does this have to do with: 
?
Vectors $\overrightarrow{AB}=B-A=(-1,-3,1)$ and $\overrightarrow{AC}=C-A=(0,-2,1)$ can be viewed as vectors starting at the origin therefore nothing change in the calculation for dot or cross product. In other words, in both cases we can consider $A$ as the origin for this purpose.