30. Last year at the Independent Learning Centre, a group of 48 students enrolled in mathematics, French, and physics. Some students were more successful than others:32 passed French, 27 passed physics, and 33 passed mathematics; 26 passed French and mathematics, 26 passed physics and mathematics, and 21 passsed French and physics; 21 passed French, mathematics, and physics.How many students passed one or more of the subjects?

The question asks for a Venn Diagram (out of 6 marks) - which is something that I can do myself.

However, what I need help with is to come up with the principle (of inclusion or exlusion) - this is out of 2 marks.

If someone could help me come up with the principle that would be awesome! thanks