It is given that R = {(a, b): a ≤ b},

It is clear that (a, a) ϵ r as a = a.

Therefore, R is reflexive.

Now let us take (2,4) ϵ R (2 < 4)

But, (4,2) ∉ Ras 4 is greater than 2.

Therefore, R is not symmetric.

Now, let (a, b), (b, c) ϵ R

Then, a ≤ b and b ≤ c

⇒ a ≤ c

⇒ (a, c) ϵ R

Therefore, R is a transitive.

Therefore, R is reflexive and transitive but not symmetric.