## Algebra 2 (1st Edition)

$A\cup B\cup C=\{2, 3, 5, 7, 11, 13, 17, 1, 4, 9, 16,8,14,20\}$
The union of sets is the set of elements that are in at least one of the sets. Hence here $A\cup B\cup C=\{2, 3, 5, 7, 11, 13, 17, 1, 4, 9, 16,8,14,20\}$