IF $A$,$B$,$C$ are finite sets then,
Number of elements in exactly one of sets $A$,$B$,$C$:$$n(A)+n(B)+n(C)-2 \times n(A \cap B)-2 \times n(A \cap C)-2 \times n(C \cap B) + 3 \times n(A \cap B \cap C)$$
Number of elements in exactly two of the sets $A$,$B$,$C$: $$n(A \cap B)+(A \cap C)+n(C \cap B) - 3 \times n(A \cap B \cap C)$$
Could somebody explain how can we prove them? I think it's something with inclusion and exclusion but am not getting how to get those results.Also I think we can have a generalized results for these kinds ?!