Conversation so far:
Who captured Zheng He?
the Ming armies at Yunnan
When was Zheng He captured by the ming armies at yunnan?
in 1381
Why was Zheng He captured by the ming armies at yunnan in 1381?
General Fu took him prisoner.

Question: How old was he when captured?
Self-contained rewrite: How old was Zheng He when captured by General Fu?