What number replaces the ◊?

4 + 7 = 1 + 10
4 + 7 + ◊ = 1 + 10 + 8

a.
3

b.
4

c.
7

d.
8

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?