Pls help me doing this

[tender jacinth]

Let m be a fixed non-zero integer. For integer a,b, we say that they are congruent modulo m iff a-b is divisible by m. We write this as a
≡
b (mod m). Let R be the relation on the set Z of integers defined by aRb iff a
≡
b (mod m). Show that R is an equivalence relation on Z.