Hands A and C are pointing exactly at hour marks. If one of these two hands is the hour hand, the minute and second hands should both be on top of each other and point at 12. Because this is not the case, B must be the hour hand. Because the minute hand points to a full minute, the second hand must point to 12.
Some of the oldest puzzles in history involve "figuring out" people's ages. They are found in ancient texts across cultures, demonstrating a long-standing fascination with imaginative and logical thinking wrapped into one, which is essentially what "figuring out" refers to. They have been a staple in collections of brainteasers since at least the medieval ages, starting with Alcuin's early ninth-century manuscript, Propositiones ad acuendos juvenes ("Problems to Sharpen Young Minds"), which contains several challenging age problems.