"Other girls are more beautiful than yours."
Translation:Alte fete sunt mai frumoase decât a ta.
First of all, there really are some people who advocate "ca" used with equality comparisons and "decât" with inequality ones. I have no idea where they take this crap from; simply talking to others reveals that a lot of speakers use "ca" for both (although no one uses "decât" for equality comparisons). Even more, the DEX itself mentions "decât" as a definition for "ca", offering the example "E mult mai frumos ca acesta.".
Other things you could consider:
Romanians are obsessed with /k/-based cacophonies, so even speakers who use "ca" in both cases, would favor "decât" in such scenarios:
Ești mai bun ca colegul tău. - cacophony here
Ești mai bun decât colegul tău. - crisis averted!
And I guess that, like in a lot of languages, there exists an attitude that longer = formal, so "decât" is a more elegant word.
I've read a bit on it in Romanian and it seems ca should be used for being similar and decât should be used for comparisons.
So if I say I am as good as you then it's Eu sunt la fel de bun ca tine. But if I say I am better than you then it's Eu sunt mai bun decât tine.
However, in my experience, people use ca in both scenarios.
I just ask myself the same and think the following could be an answer: Other girls are more beautiful "than yours" - means in this special case "the daughter (your daughter - a ta) -" not "the daughters". So the other translation (ale tale) would be correct if the inventor of this sentence would have meant the plural.
Because of the doubt we can have about " than yours " which can be
-1- than your girl,
-2- than your girlS ,
-3- than the girl of you TWO and
-4- than the girlS of you TWO,
you have also in romanian 4 solutions :
Alte fete sunt mai frumoase decât
-1- a ta ,
-2- ale tale,
-3- a voastră and
-4- ale voastre
I hope all four are accepted!