Logic Puzzle

2

Explanation: The three brothers share the same siblings. Each brother has 2 sisters, and one of them is Sally. So there must be exactly 2 girls in the family: Sally plus one other sister. Therefore, Sally has 1 other sister besides herself, which means she has 1 sister? Wait—question asks "How many sisters does Sally have?" Since there are 2 sisters total, and one is Sally, the number of sisters Sally has is 1. Correction: The correct answer is 1.