Answer
$0.000007$
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) $\frac{a^{m}}{a^{n}}=a^{m-n}$
(iii) $a^{m}a^{n}=a^{m+n}$
Write each number in scientific notation to obtain:
$=\dfrac{8(10^{-4}) \cdot 7(10^{-2})}{2(10^{4})\cdot 4(10^{-4})}
\\=\dfrac{8\cdot 7(10^{-4+(-2)})}{2.\cdot 4(10^{4+(-4)})}
\\=\dfrac{56(10^{-6})}{8(10^{0})}
\\=\dfrac{56(10^{-6})}{8\cdot 1}
\\=\dfrac{56(10^{-6})}{8}
$
Divide $56$ and $7$ together to obtain:
$=\dfrac{56}{8} \cdot 10^{-6}
\\=7 \cdot 10^{-6}
\\=0.000007$
