I think your instructor is trying to say that you don't NEED the example 2 to solve the problem, but the book is noting that those pairs are in the equivalence class of R. So if you look at the (x,y) pairs from example 2, say (1,2) and look out our relation R. So 1 is R related to 2 if and only if 2-1 is an integer. So the pair (1,2) is in the equivalence class.
As for part a) you want to find ALL possible pairs that make your relation true such that x = 1. So start with plug and chug and try to pick up a pattern. I will write out a few to check so you can see 1R1, 1R2. Does 1-1 equal an integer? Yes,it equals 0 Does 1 -2 equal an integer? Yes, it equals -1.
Part b) is a little more tricky when you are trying to consider all possible values, but it is the same idea.
In general you want to consider things like "Is it true if I use negatives? Integers? Rationals? Irrationals?" Then from what makes your relation true you can decide what "type" of numbers are related given your specific relation.