Which value goes in the empty cell?

Sophia wrote an equation to represent the revenue of a movie theater for one day. she let x represent the number of child tickets sold and y represents the nunver of adult tickets sold. if a child ticket cost $4, an adult ticket cost $6, and the total revenue for the daybwas $420, which equation could sophia use to represent the number of chikd and adult tickets that were sold?

20 ! brainliest ! add and simplify your answer.

What are the solutions of the following system? y=-2x^2 y=x-2