Question

Let Z be the set of integers and R be the relation defined in Z such that aRb if a – b is divisible by 3.

Answer 1

a are some integers, b are some integers.
now a relation among them is created with the condition that: a-b has to be divisible by 3.
eg. 6,3
6-3 is divisible by 3

but suppose 5 and 1
now 5-1 cannot be divided by three. So it does not hold the relation.