In this task, you are given two sets, and you need to count the number of elements at the union of two given sets. A Set is shown by two curly braces and comma-separated numbers inside, like {1, 2, 3}. Union of two given sets is the smallest set which contains all the elements of both the sets. To find the union of two given sets, A and B is a set that consists of all the elements of A and all the elements of B such that no element is repeated.

Set1: '{3, 4, 12, 15, 18, 20}', Set2: '{3, 13}'. How many elements are there in the union of Set1 and Set2 ?
7

Set1: '{16, 3, 6}', Set2: '{1, 5, 6, 7, 12, 13, 14, 15, 16}'. How many elements are there in the union of Set1 and Set2 ?
10

Set1: '{19, 11, 12, 15}', Set2: '{1, 2, 5, 7, 9, 17, 18, 19}'. How many elements are there in the union of Set1 and Set2 ?

11