I have the following equation

and I need to get n by itself. So far what I have done is:I=(nE)/(R+nr)

But I don't know what to do next since everything I do doesn't help me leave n by itself (and by that I mean that there must be a single instance of n in the whole equation).I*(R+nr) = nE

IR+Inr = nE

Thanks for the help.