Is there any certain ways of thinking of these examples? Or just guess and try?

a) Reflexive and symmetric, but not transitive

= abs(a-b) < 1... right? any other example?

b) Reflexive but neither symmetric nor transitive

= a-b < 1, any other type?

c) Symmetric, but neither reflexive nor transitive

= abs(a-b) = 1, any other?

d) Transitive, but neiter reflexive nor symmetric

= a < b

any other examples will be appreciated, thanks