I have the following statement to prove, for homework:
If $r ∈ \mathbb{z}$ is a solution to $ax ≡ b ($ mod $m)$, then $r + mk, k ∈ Z$, are also solutions to $ax ≡ b ($ mod $ m)$.
What does "$r ∈ \mathbb{z}$ is a solution..." mean? I assume it means $r=b$ since $b$ is usually where the modulo's solution is, but by symmetry the equation can be written as $b ≡ ax ($ mod $m)$, and now $ax$ would be the solution. Any insight on this problem is appreciated. Thank you