Answer
$0.0000002$
Work Step by Step
RECALL:
(i) Scientific notation has the form $a(10^n)$, where $1 \le a \lt 10$ and where $n$ is an integer.
(ii) $\frac{a^{m}}{a^{n}}=a^{m-n}$
Write each number in scientific notation to obtain:
$=\dfrac{8.6(10^{-4})}{4.3(10^{3})}$
Divide $8.6$ and $4.3$ together and the powers of 10 together to obtain:
$=\dfrac{8.6}{4.3} \cdot \dfrac{10^{-4}}{10^{3}}
\\=2 \cdot 10^{-4-3}
\\=2(10^{-7})
\\=0.0000002$
