Bayes gives you an ability to calculate values for different variants with hypotensis in base, not with combinations of it in base. And you don’t know by magic that mathematic has one boy, you see something in reality, don’t get data from search or question. Of course, you need to use P(“i see that mathematic said: i have one boy”), not P(“i see that mathematic has one boy”), and also not P(“i ask a question: is one of your kids a boy, and get answer: yes”).
Bayes gives you an ability to calculate values for different variants with hypotensis in base, not with combinations of it in base. And you don’t know by magic that mathematic has one boy, you see something in reality, don’t get data from search or question. Of course, you need to use P(“i see that mathematic said: i have one boy”), not P(“i see that mathematic has one boy”), and also not P(“i ask a question: is one of your kids a boy, and get answer: yes”).