The operation A U B means "A union B" for which the elements of A is combined with the elements of B
Given that
A = {3,4,5,6,7,8,9,10,11,12} and B = {8,10,12,14,16,18}
Combine all the elements, and list the repeat elements from both sets A and B (such as 8, 10 and 12) only once.
Therefore, A U B = {3,4,5,6,7,8,9,10,11,12,14,16,18}.
