The average age of a husband and a wife is 23 years…

The average age of a husband and a wife is 23 years when they were married FOUR years ago but now the average age of the husband, wife and child is 20 years(the child was born during the interval). What is the present age of the child?

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 #85908