Answer
$-\frac{4}{729}$
Work Step by Step
$a_1=12$ and we can see that the ratio of subsequent terms is $\frac{1}{10}$, thus $r=-\frac{1}{3}$
The nth term of a geometric series can be obtained by the following formula: $a_n=a_1\cdot r^{n-1}$, where $a_1$ is the first term and $r$ is the common ratio.
Hence here: $a_8=12\cdot(-\frac{1}{3})^{8-1}=12\cdot-\frac{1}{2187}=-\frac{4}{729}$
