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Let's break it down carefully.
- Sally is a girl.
- She has 3 brothers.
Now, consider the statement: "Each brother has 2 sisters."
Who are the sisters of Sally’s brothers?
The brothers share the same siblings — the same family. So Sally and her sisters are the sisters of each brother.
We know Sally is one sister. Let the number of other sisters (besides Sally) be $ x $. So total sisters = $ 1 + x $.
Each brother has 2 sisters, so:
$$ 1 + x = 2 \Rightarrow x = 1 $$
So there is 1 other sister besides Sally.
Therefore, Sally has 1 sister (besides herself), meaning 2 sisters total — but wait — when we say "how many sisters does Sally have?", we don’t count herself. So:
- Total girls in the family: Sally + 1 other = 2 girls
- So Sally has 1 sister.
✅ Let’s verify:
- Sally: 1 sister (the other girl), 3 brothers ✔️
- Each brother: 2 sisters (Sally + the other girl), 2 brothers (the other 2 brothers) ✔️
Yes, consistent.
Answer: Sally has 1 sister.