Would it be:
世界中10の最も話し言語
or
世界で10最も話されて言語
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Sign up to join this communityLet's start with 話されている "are spoken".
We'll use that as a relative clause to modify 言語 "language":
話されている言語
languages that are spoken
And we'll add 最も "most":
最も話されている言語
languages that are spoken the most
= the [most spoken] languages
And 世界で to make the scope "in the world":
世界で最も話されている言語
the most spoken languages in the world
Last, we insert 10の to say how many of the most spoken languages:
世界で最も話されている10の言語
the ten most spoken languages in the world