I'm trying get excel to reverse a calculation so that I can type in the answer and excel comes up with a list of possible values which satisfy my equation.

So I have;
(X*Y*Z)/(P*Q*R) = 7.2 (+/- 0.05)

and X,Y,Z,P,Q,R represent natural #'s
then there are a few more restriction for the variables as they all have to be below 30 and above 12.

If your wondering what this calculation is for, it is to find possible values for a reduction gear box.

Thanks