The answer is 7/69.
There are 8 black-haired children among 24 children. The probability of randomly selecting black haired children for the first time is:
P1 = 8/24 = 1/3
Now, there are 7 black-haired children left among 23 children. The probability of randomly selecting black haired children for the second time is:
P2 = 7/23
Since we want both of these events to occur together, we will multiply their probabilities:
P = P1 * P2 = 1/3 * 7/23 = 7/69