In this context, "favorite" is singular because each person is stating their individual favorite subject. Therefore, it would be correct to say "Physics is my favorite subject" and "Math is my favorite subject" as each individual is referring to their own favorite subject.
In this context, "favorite" is singular because each person is stating their individual favorite subject. Therefore, it would be correct to say "Physics is my favorite subject" and "Math is my favorite subject" as each individual is referring to their own favorite subject.