Answer:
Probability of both red =3(182)=3(18!2!16!)=3153
Step-by-step explanation:
Let Ai be the event in which the i-th ball you grab is red. For the first ball you choose, you have 3 red marbles out of a total of 18. Therefore,
P(A1)=318.
For the second marble you grab, given that you already took a red one, that is, given A1, you have 2 red balls out of a total of 17, then
P(A2∣A1)=217.
Finally,
P(A1∩A2)=P(A1)P(A2∣A1)=318217=151.
