A family consists of grandparents, parents and three grand children

A family consists of grandparents, parents and three grand children. The average age of the grandparents is 67 years, that of the parents is 38 years and that of the grandchildren is 6 years. What is the average age of the family?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #5053