Given:

A = 12,4,5,7,8)

B = (3,5,8,9)

What is A UB?

AUB = {3,4,5,7,8,9,12}

Step-by-step explanation:

The union of the 2 sets contains all the elements in both sets except where there are duplicates, like here where we have 2 5's and 2 8's, only one is included.

A u B = { 3, 4, 5, 7, 8, 9, 12 }

Step-by-step explanation:

The union of sets u is the set of elements in set A, or set B, or both

Thus

A u B = { 3, 4, 5, 7, 8, 9, 12 }