solution:
R = {(1, 2), (2, 1)}
(x, x) ∉ R. R isn’t reflexive.
(1, 2) ∈ R and (2,1) ∈ R. R is symmetric.
Once more, (x, y) ∈ R and (y, z) ∈ R then, at that point (x, z) doesn’t suggest to R. R isn’t transitive. Thusly, R is symmetric however neither reflexive nor transitive.