The probability of choosing a man first is 35/50.
The probability of choosing a woman first is 15/50.
Two situations:
Choose men first, then choose women, that is 35/50* 15/49, because after choosing boys, the probability of choosing girls becomes greater, as long as you choose from 49 people in the class.
Similarly, a woman was selected first, and then a man was selected 15/50*35/49.
Just add up the probabilities of the two situations.
The probability problem is as complicated as it can be. In high school, we should make clear the difference between sorting and non-sorting. It is best to read relevant textbooks. If you don't know, you can read more books and do the above exercises according to your own ideas.