If P+Q means P is the mother of Q, P-Q means P is the brother of Q, P%Q means…

Concept

In coded blood-relation puzzles, each operator is a single generation link: '+' = mother of, '-' = brother of, '%' = father of, and '×' (also printed as '*') = sister of. A person's maternal uncle is, by definition, the brother of that person's mother — so an expression names X as Y's maternal uncle only if it reduces to 'X is the brother of some M' and 'M is the mother of Y' for the same intermediate person M.

Application

1. In P-M+N×Q, the first link P-M gives: P is the brother of M.

2. The second link M+N gives: M is the mother of N.

3. The third link N×Q gives: N is the sister of Q, so N and Q share the same mother — meaning M, already fixed as N's mother, is also the mother of Q.

4. Combining these: M is the mother of Q, and P is the brother of M, so P is the brother of Q's mother — exactly the maternal-uncle relationship the question asks for.

Cross-check

Draw the family tree implied by the chain: M and P are siblings (one generation above Q); M has two children, N and Q, since N is Q's sister. P, being M's brother, sits in the same generation as Q's mother and is male, which confirms P is Q's maternal uncle.

Why the other expressions fail

• Q+N-M+P traces Q as the mother of N, N as the brother of M, and M as the mother of P — this makes Q an ancestor of P through M, the reverse relationship, not P as Q's maternal uncle.

• Q+N%S-L relates only Q, N, S and L; it never introduces P at all, so it cannot express any relationship between P and Q.

• M+L-O+S relates only M, L, O and S; it contains neither P nor Q, so it is unrelated to what the question asks.