How old are these bones?

Question

The radioactive element​ carbon-14 has a​ half-life of 5750 years. A scientist determined that the bones from a mastodon had lost 73.9​% of their​ carbon-14. How old were the bones at the time they were​ discovered?

Answer 1

The percent remaining is (100 - 73.9)% = 26.1%

You can set up the solution as

100 (0.5)^t/5750 = 26.1,

with t in years. Take natural log on both sides.

ln100 + (t / 5750)ln(0.5) = ln26.1

You should be able to solve for t and finish from here.