The half life of carbon-14 is about 5760. If a bone sample only has 15% carbon-14 remaining, determine the age of the bone.

This question throws me off cause of the percent, if it was in mg's I could do it no problem.

The only part of the equation that I know is (1/2)^(x/5760) and I don't know where to put the .15 in cause it's not a measurable amount (ie. in mg's).

All I got is y=a(1/2)^(x/5760)

If anyone can show me what to do with the 15% it would greatly be appreciated. (I assume I need to find y and a, so I can solve for x)

Would it be something like .15=1(1/2)^(x/5760)?