Since we don't care about the order in which we select people, we will use the combinatoric approach, rather than permutations.
Since we want to select 3 teachers from a total of 8, this is the notation to select 3 teachers from 8 (objects).
Teachers :

Similarly, students :

Now, since we want both at the same time, we will need to multiply both to yield your final answer:

different ways.