So far this semester, Warren is averaging a score of 72 points on math tests, which is 20% lower than his average last semester. What was the average of his scores last semester?

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?