A math problem ..

The three students in Class One happen to have the same speech number, so we can regard the three students in Class One as a whole.

Then one * * * has three! *8! grow

We can find out the probability that the phonetic serial numbers of two students in Class Two are not connected.

So I also regard the two people in Class Two as a whole.

One * * * has three! *2! *7! grow

So the probability that the phonetic serial numbers of two students in Class Two are not connected is 1-(3! *2! *7)! /(3! *8! )=3/4