Question

{8} {7, 8, 9}

Answer 1

It's so set-ty

Answer 2

Let a={8}, b={7,8,9}, then a is a subset of b and b is a superset of a. We know that there exists a surjection from b to a, and an injection from a to b. But we know that there exists no surjection from a to b., therefore there exists no bijection between the two.