Which operation between 2 polynomials will not always result in a polynomial?

Need this asap if anyone can i would be very grateful. if you could show workings that would really

Aculinary club earns $1360 from a dinner service. they sold 45 adult meals and 80 student meals. an adult meal costs twice as much as a student meal. what is the cost of an adult meal?

Me : julio wears a blue shirt every 3 days. larry wears a blue shirt every 4 days. on april 11, both julio and larry wore a blue shirt. what is the next date that they will both wear a blue shirt?