Task: Reasoning / Mathematical Reasoning
User instruction:
The following describes the life of a mathematician born in ancient Greece.  
Blessed by the gods, he spent one-sixth of his life as a boy. After another twelfth had passed, a beard began to sprout on his face. A further seventh of his life later, he married a beautiful woman, and five years into the marriage he welcomed a precious son. Alas! The poor child lived only half as long as his father’s lifespan. Overwhelmed by grief, the mathematician devoted the next four years to number theory to console himself, and then his life came to an end.  
How old was he when he died?

Evaluation criteria:
Based on the given lifespan, the age at death is 84.
The given problem requires using a common denominator (least common multiple).
In the final answer, append the unit ‘years old’ to the age at death.