been working on this problem for a while and am stuck! equation is Q=(N-S)/N, I started by multiplying both sides by N and got QN=N-S, then divided both sides by Q and got N=(N-S)/Q, this is where I am stuck am not sure how to "get rid of" the N in N-S. The answer in the book is N=S/(1-Q), but I can not get it

Please Help!