I Q test question I can’t figure out

Question

There are 40 students 40% are taking physic and 30% are taking chemistry.10% are taking neither how many student are taking neither. Now I know the answer I would like to know how they arrived at it. 16

Answer 1

I think that you mean 10% are taking both Physics and Chemistry (that's 4)

16 are taking Physics. So, 16-4 = 12 are taking Physics, but not Chemistry.

12 are taking Chemistry. So, 12-4 = 8 are taking Chemistry, but not Physics

So, 12 + 8 + 4 = 24 are taking one or both classes.

That leaves 40 - 24 = 16 that are taking neither class.

You could also solve this problem using a Venn Diagram, if you are familiar with that concept.