The equation used to calculate how much remains of a sample based on its half-life is y=a\cdot\left(\frac{1}{2}\right)^{\ frac{t}{h}}y=a⋅( 2 1 ​ ) h t ​ . A is the amount that you started with, t is the time that has gone by and h is how many half-lives have happened. Given that a sample is 50g that has a half-life of 20 years, how much of the sample remains after 15 years?