Would "The red pencils are Andrew's" be acceptable?
Yes, it's actually the best translation.
I've reported the version using Andrei's.
"The red pencils are Andrew's" should be the default solution since it is both correct and closest to the original.
Not accepted 1-7-2018.
Still not accepted 24/08/2018
Still not accepted 06/10/2018
Still not accepted 10/29/2018
Still not accepted 2019/02/06
Still not accepted 16/3/2019... and reported...
Still not accepted 2019-May-09.
is lui mandatory? Would creioanele roșii sunt ale Andrei be enough?
"lui" is mandatory. "Ale" is just a preposition. "Ale mele / ale tale / ale lui / ale ei / ale noastre / ale voastre / ale lor" = mine / yours / his / hers / ours / yours / theirs.
Thank you, so they always go hand-to-hand. I thought you could leave out the pronoun if the noun is explicit.