What is $x-y$ given $x/y$

Question

If I know $x$ divided by $y,$ how can I work out $x-y$ from that? Suppose $x>y.$ Is this even possible? Thanks in advance.

Answer 1

Note that $\frac{4}{2} = \frac{2}{1}$, but $4-2=2 \neq 1 = 2-1$.

So the answer to your question is negative