how much greater is 7.9\times 10^{7}7.9×10 7 than 8.7\times 10^{5}8.7×10 5 ? express your answer using either standard notation or scientific notation.

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?