Answer
$-0.0000149$
Work Step by Step
For solving this, we will use the formula for the $nth$ term of the geometric series. $a_{n}=a_{1}\times r^{n-1}$.
Then put correct value for $n$ to solve.
$a_{30}=8000 \times (-\frac{1}{2})^{30-1}=-0.0000149$