Logic Puzzle

To determine how many sisters Sally has, we can break down the information given in the problem step by step.

1. Identify the number of brothers Sally has. According to the problem, Sally has 3 brothers.
2. Each of Sally's brothers has 2 sisters. Since Sally is one of the sisters, the other sister must be the same for all brothers. Therefore, the other sister is the same person, not a different sister for each brother.

Let's denote the sisters as follows:

• Sally is one sister.
• Let's call the other sister ( S ).

Since each brother has 2 sisters and Sally is one of them, the other sister must be ( S ). This means that Sally and ( S ) are the only two sisters.

Thus, Sally has 1 sister.

The answer is (\boxed{1}).