If A + B means A is the brother of B, A - B means A is the sister of B, and A × B means A is the father of B, what is the relationship of C to D if C + D and D - C are true?
If A + B means A is the brother of B, A - B means A is the sister of B, and A × B means A is the father of B, what is the relationship of C if A + C - B = true?