It is given that A and B are two sets such that A⊂B.
Since B is the superset of A, then all the elements of A are in B.
Therefore, A∪B=B.
If A and B are two sets such that A ⊂ B, then what is A ∪ B?
If A and B are two sets such that A⊂B, then write B' - A' in terms of A and B.