Math question about stat

Question

Suppose a jar contains 8 red marbles and 12 blue marbles. If you reach in the jar and pull out 2 marbles at random at the same time, find the probability that both are red.

Answer 1

20 marbles total. 8 red marbles

Event A = pick red marble on first draw

Event B = pick red marble on second draw

P( A and B) = P(A) * P(B|A)

P(A) = 8/20 = 2/5

Leaves you with 7 red marbles and 19 marbles total after first draw

P(B|A) = 7/19

P(A and B) = 2/5 * 7/19 = 14/95