What this means is that is you flip the coin 12 times and follow that with a role of 1 die, a head and a 2 out to come up once. That does not mean it will. It only means that it should.
I think it would be 19 because if you take 100-5 it would be 95 and divide 95 by 19 you would get 5 so each student got 5 cookies and there was 19 students