Final answer:
The simple predicate of the sentence is 'are interested'
Step-by-step explanation:
The simple predicate of the sentence 'Howard and Sandy are interested in school politics' is 'are interested'.
A predicate is the part of a sentence that expresses the action or state of being of the subject. In this sentence, 'are interested' is the predicate because it describes what Howard and Sandy are.
Another example of a predicate is: 'She plays the piano.' Here, 'plays' is the predicate because it expresses the action of the subject 'She'.
Learn more about Parts of speech