Question

If A = {2, 4, 6, 8, 10} and B = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, what is A U B?

Answer 1

AUB is the set of all the elements present in A and B.
Therefore, AUB ={1,2,3,4,5,6,7,8,9,10}

Answer 2

the union set is the set that contain all the elements present in either one of the two sets
here A is included in B
so the union is the set B itself