# Applying set operations on congruent mod relation

I've been asked a question to solve about congruent modulo. But the question is very different than another congruent modulo questions I have seen so far. It wants me to apply set operations on it. Can you give me a hint how to solve this question, not the answer. Thanks in advance...

Question:

https://ibb.co/SKQYCys

It is worth stating the following result. For arbitrary $$n \in \mathbb{N}$$ let us denote the congruence modulo $$n$$ by $$R_n$$; it then holds that:
$$R_m \cap R_n=R_{[m,n]}$$
where $$[m,n]$$ denotes the least common multiple of $$m$$ and $$n$$.