Answer
$0.3$
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:
$=\dfrac{3.9(10^{-4})}{1.3(10^{-3})}$
Divide $3.9$ and $1.3$ together and the powers of 10 together to obtain:
$=\dfrac{3.9}{1.3} \cdot \dfrac{10^{-4}}{10^{-3}}
\\=3 \cdot 10^{-4-(-3)}
\\=3(10^{-4+3})
\\=3(10^{-1})
\\=0.3$
