Answer
$7 \times 10^{-3}$
Work Step by Step
$\dfrac{a^m}{a^n}=a^{m-n}, a\ne0$
Divide the corresponding parts while using the rule above to obtain:
$=\dfrac{3.5}{5} \times \dfrac{10^{6}}{10^{8}}
\\=0.7 \times 10^{6-8}
\\=(7 \cdot 10^{-1} \times 10^{-2}
\\=7 \times 10^{-1+(-2)}
\\=7 \times 10^{-3}$
