MiniMax M2.7
Sally has 1 sister.
Reasoning
- Sally is a girl, so she counts as one of the sisters in the family.
- Each of her three brothers has exactly two sisters.
Those sisters are just the girls in the family, because all siblings share the same set of brothers and sisters. - Therefore the family contains exactly 2 girls (two sisters).
- Since Sally is one of those two girls, the other one is her sister.
So Sally has just one sister.







