$R$ relation $aRb \leftrightarrow a/b = q^2$ where $q$ is in $Q$. We need a bijection $X→Y$ where $X$ is the set of all Equivalence classes and $Y$ is the set of all sets $P$ that consists only of prime numbers and $|P|$ is not infinity. For example, an element $P$ of $Y$ is $\{2,3,5\}$.
I am stuck here. I have found the equivalent classes but I can't seem to find a bijection here. Any tips? Thanks.