Question 178382
{{{I=nE/(nr+R)}}}
:
{{{I(nr+R)=nE}}}multiplied both sides by (nr+R)
:
{{{Inr+R=nE}}}distributed left side
:
{{{R=nE-Inr}}}subtracted Inr from  both sides
:
{{{R=n(E-Ir)}}}factored out n on right side
:
{{{n=R/(E-Ir)}}}divided both sides by (E-Ir)