If the half-life of an unstable isotope is 10,000 years, and only 1/8 of the radioactive parent remains in a sample, how old is the sample?

Have in mind that a radioactive half-life is the amount of time it takes for half of a sample to decay. So, if the amount remaining after x half-lives is (1/2) ↑x times the amount you started with. So for 1/18 of radioactive parent then (1/2) ↑6 equals 30,000 years