2 trains leave at the same time. One east and one west at a speed that is 10 mph slower. In 1.5 hrs, the trains are 171 miles apart. Find the speed of each train

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?