How many liters each of a 55% acid solution and a 75% acid solution must be used to produce 40 liters of a 65% acid solution? (Round to two decimal places if necessary.)

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?