George and Carmen went on a bicycle trip. They took a bus to their starting point, and then biked the rest. They traveled 300 kilometers in total, and they biked 70 kilometers more than they were bussed.

Let x = kilometers traveled by bike and y = kilometers traveled by bus.

You just purchased two coins at a price of $670 each. because one of the coins is more collectible, you believe that its value will increase at a rate of 7.1 percent per year, while you believe the second coin will only increase at 6.5 percent per year. if you are correct, how much more will the first coin be worth in 15 years?