I have answer please help I dont know how to get to it

Exercise#3: 3.1. Let r be the relation on the set of integer numbers (Z) such that arb if and only if a +b is even. Is r an equivalence relation? 3.2. Let r be the relation on the set of integer numbers (Z) such that arb if and only if a +b is odd. Is r an equivalence relation? NOt regiexive 3.3, Let A = {1, 2, 3, 4, 5), and let be an equivalence relation on A. Find the [1] and [3] on R. Continue on next page