"are promoted at the festival" --- this is the predicate Its easy to find the predicate- just know what you are talking about. Here you are talking about "Welsh language, literature, music and culture". So they are the subject. The remaining sentence is the predicate. Hope I helped!
are promoted at the festival = complete predicate
The complete predicate in the sentence is "are promoted at the festival," which explains what happens to the subject. The subject is "Welsh language, literature, music, and culture." The complete predicate includes the verb and additional information describing the action.
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