Lilly takes a train each day to work that averages 35 miles per hour. On her way home, her train ride follows the same path and averages 45 miles per hour. If the total trip takes 2.5 hours, which equation can be used to find n, the number of miles Lilly’s home is from her work?

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.