Every day Amy travels 30 miles one-way to work. The park-and-ride where she catches the train is 5 miles from her home. The average speed of the train is 15 mph faster than the average speed in her car. Assuming she has no wait time for the train, her one-way trip takes 45 minutes. Find the speed of the car.

The answer is -pie over 2

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.