Question

Set a contains 21 elements a B contain 16 element and five element our common percent ANB how many elements are the ANB

Answer 1

We will have the following:

For the information provided we will have that A unit B has the following number of elements:

$n_EA\cup B=21+16-5\Rightarrow n_EA\cup B=32$

So, the number of element in A union B is 32 elements.