Proposition 24
If an even number is subtracted from an even number, then the remainder is even.
Let the even number BC be subtracted from the even number AB.
I say that the remainder CA is even.
Since AB is even, therefore it has a half part. For the same reason BC also has a half part, so that the remainder CA also has a half part, and CA is therefore even.
Therefore, if an even number is subtracted from an even number, then the remainder is even.
Q.E.D.