Family composition puzzle (brothers and sisters): Use simultaneous conditions for sons and daughters. Each daughter has as many brothers as sisters. Each son has twice as many sisters as brothers. Find the number of sons in the family. Choose the correct value.

Let b = number of sons, g = number of daughters.

Translate conditions For a daughter: brothers = b, sisters = g − 1 ⇒ b = g − 1. For a son: sisters = g, brothers = b − 1 ⇒ g = 2(b − 1).

Solve From b = g − 1 ⇒ b − 1 = g − 2. Plug into g = 2(b − 1): g = 2(g − 2) ⇒ g = 2g − 4 ⇒ g = 4. Then b = g − 1 = 3.

Final Answer 3 sons