Answer:
Sang and played
Here is my explanation:
The subject is the noun, or the main focus of the sentence. The predicate is the verb, or what the person/thing is doing in the sentence.
So in this sentence, Trevor is the subject, or the main focus of the sentence. And what did Trevor do at camp? He sang and played the guitar. So therefore, the predicate of this sentence is "sang and played".
I hope this helped! Have a good rest of your day!