Answer
{$1;2;3;4;6;9;12;18$}
Work Step by Step
The union of two sets consists of the elements that are in the first set, in the second set or in both sets:
{$1;2;3;4;6;12$}}$\cup${$1;2;3;6;9;18$}$=${$1;2;3;4;6;9;12;18$}
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