Answer
$2.11\times10^{9}\,years$
Work Step by Step
$\frac{1}{8}=\frac{1}{2}\times\frac{1}{2}\times\frac{1}{2}$
Three half-lives are needed for the amount of sample to reach one-eighth of its initial amount.
That is, $t=3\times703\,million\,years=2.11\times10^{9}\,y$
