Translation:The third, fourth, and fifth baskets are pretty.
Shouldn't "basket" be singular here, seeing as we're ordering individual objects in some way?
Mi estas komenkanto so I don't know if this idea will translate from English to Esperanto but immagine saying "the 3rd 4th and 5th basket is pretty." That doesn't sound right, does it?
I am not great with grammar so hopefully someone can answer more clearly at another time. As I see it, you are denoting which baskets are beautiful out of a group, thus creating a separate group: the three baskets you think are beautiful. So instead of it being: "The third basket is pretty. The fourth basket is pretty. The fifth basket is pretty." ... It's more like: "This group of baskets is beautiful." I hope this helps somewhat. :)