z/m − z/n =1, if m≠n

Answer 1

I assume you want to solve for z.
z(1/m - 1/n) = 1
z = 1/(1/m - 1/n)

Oh, ok. let's make that a bit prettier.
1/m - 1/n = n/mn - m/mn = (n-m)/mn
so, z = mn/(n-m)