Question 35943
If you want to solve for R, then you must eliminate or undo everything that has been done to R.  In this problem, R is multiplied by P and T.  In order to "undo" multiplication, you must DIVIDE both sides by P and T.

{{{I= P*R*T}}}

{{{I/(P*T) = (P*R*T)/(P*T)}}}


The P and T divide out, and you are left with 
{{{I/(P*T) = R}}}


R^2 at SCC