New to combinatorics (second lesson in the course). I'd like you to explain to me how to solve the following problem.
We have two classes of students, A and B.
In class A: every student except Dan knows exactly 12 students from class B, Dan knows exactly 8 students from class B
In class B: every student knows exactly 8 students from class A we know that class B contains 43 students
We need to find the number of students in class A.
To be honest, I don't know where to start -
I know that class A contains more than 8 students (if 8 then in this case every student in a knows 43 students in class b).
I feel that we need to apply the pigeonhole principle to solve this problem but I don't know where.
Please help me understand how to address this kind of problem.