If P - Q means P is the sister of Q, P + R means P is the mother of R, and R × S means R is the daughter of S, what is the relationship of Q to S in the expression P - Q + R × S?
If M × N means M is the mother of N, N - O means N is the sister of O, and O + P means O is the brother of P, what is the relationship of M to P in the expression M × N - O + P?
If X - Y means X is the brother of Y, X + Z means X is the sister of Z, and Y × Z means Y is the father of Z, what is the relationship of X to Z in X - Y + Z?