<span>Two cars start moving from the same point. one travels south at 48 mi/h and the other travels west at 20 mi/h. at what rate is the distance between the cars increasing four hours later? so its 400%</span>
The 10$ is added on because it's a one time exchange and the 8 is multiplied by the x because for every hour you add 8$ to the price and y is the total price at the end depending on x.
