energy - does $Q_AV_{AB}=Q_BV_{BA}$ in this case

Sorry fo unclear title but I can't find any suitable on for this question. Here is what my text book says about how to find out the energy of a system of charge of n particle.

What I don't know is if it ok to take that $R_{31}=R_{13}$. I means to make calculation first we must take an reference frame so it's obviously that $R_{31}=-R_{13}$