Answer is '5'

Because the elements of A U B are 2,3,4,5,6. The count would be 5.

len(list(x for x in {1,2,3,4,5,6} if x in {2,3,4,5,6,7,8}))

        int count=0;
  int a[]={1,2,3,4,5,6};
  int b[]={2,3,4,5,6,7,8};
 for(int i=0;i<a.length;i++)
    {
for(int j=0;j<b.length;j++)
{
    if(a[i]==b[j])
    {
        count++;
    }
}

} System.out.print(count); } }

Look under Set Theory Symbols, to understand the question. https://www.rapidtables.com/math/symbols/Basic_Math_Symbols.html