Thread: inclusion exclusion principle help!

if A,B and C are finite sets with the following properties:
B has 2 more elements than A;C is twice as big as B;
AnB is the same size as AnC;B and C have no elements in common.
prove that |AnBnC| is divisible by 2 (i.e. has an even number of elements)

Originally Posted by university

if A,B and C are finite sets with the following properties:
B has 2 more elements than A;C is twice as big as B;
AnB is the same size as AnC;B and C have no elements in common.
prove that |AnBnC| is divisible by 2 (i.e. has an even number of elements)

Because "B and C have no elements in common", .
Zero is an even number.