On earth, the ratio of carbon 14 to carbon 12 $t$ years after the death of an organism is given by $$R =\frac{1}{10^{12}}e^{-t/8223}.$$
On your vacation you find a beautiful ancient woven basket where the ratio of carbon 14 to carbon 12 is $0.72\times 10^{-12}$. It is approximately years old.