1. The problem statement, all variables and given/known data proof (a/b)/(c/d) = (a/b).(c/d)-1 = (a.b-1).(c.d-1)-1 = (a.b-1)(d.c-1)=(a.d).(b-1.c-1) = (a.d).(b.c)-1 = (a.d)/(b.c) 2. Relevant equations 3. The attempt at a solution the other way to proof (a/b).(c/d)-1 = [(a.b-1)/(c.d-1)].(d/d-1) = (a.d.b-1)/(c.d.d-1) =(a.d.b-1)/c = (a.d)/(b.c) which one is better proof ?