Rick has just celebrated his 15th birthday. His oldest brother is twice his age, and his middle brother is a third of the oldest brother's age. The smallest brother is half the middle brother's age. If the youngest brother is 2 years younger than the smallest brother, how old, in years, is the youngest brother? Let's think first. Chain of thought:
Rick's oldest brother is 15 years * 2 = 30 years old. This means the middle brother is 30 years / 3 = 10 years old. The smallest brother is therefore 10 years / 2 = 5 years old. So the youngest brother is 5 years 2 years = 3 years old.
Therefore, the answer is 3.