Given : x and y are positive integers.I. Given : 20 < xIt says nothing about y.∴ I alone is not sufficient.II. Given : y > 17It says nothing about x.∴ II alone is not sufficient.I & II.x > 20, and y > 17For y = 18, 19 and 20, y < x.But for x, y > 21, we can’t say definitely which one is greater. e.g. x = 22 and y = 25, y > x.∴ I & II together are not sufficient.