What is the measurement of BC? please help and explain i dont understand these

Sasha drank 8 bottles of water everyday for a week. how many bottles of water did she drink in total?

How many solutions does the nonlinear system of equations graphed below have?

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?