I accept that there's no answer that YOU could possibly give, but I could certainly explain it to your kid for you.https://twitter.com/soncharm/status/1128787224542232583 …
To get deeper you then have to explain why his method and answer were correct as an answer to a mathematical question but what was being asked wasn't a mathematical question which is a very complex subject to explain to kids - some adults in this thread don't even understand it