The calculation of the answer to this question should not be understood that way. I think it should be understood correctly. The question says that there are three people who do not participate in the program, then there are eleven people who participate in the two programs, that is, these eleven Everyone should participate in at least one. Ten people dance, that is to say, only one person does not dance, then he must sing (because each of these eleven people has at least one show), in this case, among the nine people who sing, this one does not dance, and the remaining eight sing The ones who don’t dance must be dancing (because the one who doesn’t dance is one of the nine singing ones). So the answer is 9-1=8. As for ten plus nine minus eleven, I don't agree. There are a total of fourteen people. That calculation method can easily mislead children.