Answer
$4,000,000$
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:
$=\dfrac{6(10^{3})}{1.5(10^{-3})}$
Divide $6$ and $1.5$ together and the powers of 10 together to obtain:
$=\dfrac{6}{1.5} \cdot \dfrac{10^3}{10^{-3}}
\\=4 \cdot 10^{3-(-3)}
\\=4 \cdot 10^{3+3}
\\=4(10^6)
\\=4,000,000$
