Interesting spread of perspectives shown here. I do a lot of outreach work at Perth observatory and agree completely that an answer of 2457 megaparsecs isn't very edifying. But the key is to provide multiple answers, and not get hung up on having too many significant figures. I think if you're questioner's eyes haven't glazed over it's a great opportunity to talk about cosmological redshift and light years. Being a geo I usually relate it to whatever the dominant megafauna were roaming our planet at the time the light left, but in this case - twice the age of the earth will do, or half the time since the Big Bang.
Condescension, arrogance or irritation are never tools I would use when talking to friends, or for that matter anyone who asks a genuine question in good faith. Regardless of how superior we astronomers are in every way, there's a good chance anyone you're talking to knows more about something than you do.
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