Just need to know the elements of (A n B)

{ 1,2}

Step-by-step explanation:

The ∩ means intersection, or what is in common for the two sets

The intersection of A and B is what is in the overlapping circles

The intersection of A and B is { 1,2}

19

Step-by-step explanation:

We know there are 25 boys, meaning if we divide it by 5 we can figure out that the number of girls is 15.

25 - 16 = 9 boys went sailing

15/3 <-- To find out how many of the girls went sailing

dividing it by 3 would also us to have one third going climbing at the remaining 2/3 going sailing

10 girls went sailing

10 + 9

=19