@NfNitLoop on Twitter@NfNitLoop ("Cody C. #BLM") replied to a tweet by @hiro_asari:
@hiro_asari I interpret that as X+Y=13, but IMO it's ambiguous.
If "X and Y" is a common collection-of-things, then it seems very likely X+Y=13, as in "Thirteen boys and girls."
Can disambiguate with "N Xs and N Ys".