If X + Y means X is the daughter of Y; X - Y means X is the brother of Y; X %…

In coded blood-relation puzzles, each operator directly encodes a family relation: ‘+’ = daughter of, ‘-’ = brother of, ‘%’ = father of, and ‘x’ = sister of. To identify a compound relation like niece, chain the equations through the shared letters, track each person's gender from wherever they appear as the subject of an operator, then combine the links into a family tree.

1. I x C → I is the sister of C, which establishes I as female.

2. C + N → C is the daughter of N; since I is C's sister, I is also N's daughter.

3. N - J → N is the brother of J, so N and J are siblings (share the same parents).

4. Combining these: I is N's daughter, and N is J's sibling — so I is the daughter of J's sibling, which is exactly the definition of niece. Hence ‘I x C + N - J’ means I is the niece of J.

Cross-check: rearranging the same letters into ‘I x C - N % J’ gives I as C's sister, C as N's brother, and N as J's father — that puts N (and so I) in J's parents' generation, making I J's aunt, not niece. Only ‘I x C + N - J’ keeps I one generation below J (daughter of J's sibling), confirming the niece relation.