Answer
$a_8=\dfrac{3}{32}$
Work Step by Step
Recall:
In a geometric sequence, the $n^{\text{th}}$ term $a_n$ is given by the formula:
$$a_n=a_1 \cdot r^{n-1}$$
where
$a_1$=first term and $r$=common ratio
The given geometric sequence has $a_1=12$ and $r= \frac{1}{2}$.
Use these values and the formula above to obtain:
\begin{align*}
a_8&=a_1 \cdot r^{8-1}\\
a_8&=12 \cdot \left(\frac{1}{2}\right)^7\\
a_8&=12 \cdot \frac{1}{128}\\
a_8&=\frac{3}{32}
\end{align*}
