Answer
A U C = {1,3,4,5,6,9}
Work Step by Step
U means union. With sets, union means to combine all of the elements in both sets.
A={1,3,4,5,9}
C={1,3,4,6}
To get A U C list all elements from each set in one group:
1,3,4,5,9,1,3,4,6
and remove any duplicates:
1,3,4,5,9,6.
Finally put them in order for readability (although this step is not required).
{1,3,4,5,6,9}.
