An example of a compound predicate in the sentence "Julie and her mother live in France and speak English" is the end portion, "live in France and speak English." The predicate is the part of the sentence that makes a statement about the subject. It tells what the subject is doing or what is happening to the subject.
A simple predicate tells one thing about the subject. An example is "Julie lives in France." The simple predicate, "lives in France," tells one thing about Julie, the subject.
A compound predicate tells at least two things about the same subject. It does not repeat the subject. In the original sentence, "live in France and speak English" is the compound predicate since it tells two things about the subjects "Julie and her mother."