"Girls are pretty."

Translation: Dívky jsou hezké.

[Jim58190]

Why is "Holky jsou hezká" not accepted?

[VladaFu]

Holky are feminine plural (nominative case), feminine plural nominative of hezký is hezké. Hezká is either feminine singular or neuter plural.

[SGuthrie0]

"Holky jsou hezké" is accepted.

[Shannon548166]

What is the difference between Dívky and Holky?

[AntonBaidzionak]

...and děvče

[VladaFu]

děvčata

[VladaFu]

See https://forum.duolingo.com/comment/27749621

[Ruby56531]

please tell me what endings to use for adjectives like why is it "hezké" and not "hezki" or "hezky"

[BoneheadBass]

As with your question about demonstrative pronouns in another discussion, the adjective needs to match the noun it modifies in gender, number, and case. See the declension table for hezký at a different, but also useful, site: https://en.wiktionary.org/wiki/hezk%C3%BD.