Answer:
5
Step-by-step explanation:
The equation says y equals 5. I attached a graph below:
If we assume the club membership includes

then the blanks in the Juniors circle must be filled in with 6 and 8 (with the 8 going in the overlap with girls). The remaining blank in the Girls circle must be filled in with 12, the number of senior girls. The blank outside both circles is the number of senior boys (members who are not juniors and not girls), 16.
What happened in the first questions doesn't influence the final question, so the probability is simply 1/5 = 0.2
6 because that's the gcf of those numbers no matter id its simplified or not :)