# Math Help - Congruence

1. ## Congruence

Prove that:

If a ≡ b (mod n) and m|n then, a ≡ b (mod m).

2. Originally Posted by porterhv
Prove that:

If a ≡ b (mod n) and m|n then, a ≡ b (mod m).
you are asked to prove if $n \mid (a - b)$ and $m \mid n$ then $m \mid (a - b)$