The price of admission at a movie theater is $6 for an adult and $4 for a child. in one day, the movie theater sold 80 tickets and made $420. how many adults and how many children bought tickets to the movie theater that day?

x + y = 80,
6x + 4y = 420

which is a solution of the system of equations, and what does it represent?
(20, 60); 20 adult tickets and 60 child tickets
(30, 50); 30 adult tickets and 50 child tickets
(40, 40); 40 adult tickets and 40 child tickets
(50, 30); 50 adult tickets and 30 child tickets