7. a publisher sells 10^6 copies of a new science fiction book and 10^3 copies of a new mystery book. how…

Explanation:

Step1: Identify the quantities

The number of science - fiction books sold is $10^{6}$, and the number of mystery books sold is $10^{3}$.

Step2: Calculate the ratio

To find out how many times more science - fiction books were sold than mystery books, we divide the number of science - fiction books by the number of mystery books. Using the rule of exponents $\frac{a^{m}}{a^{n}}=a^{m - n}$, we have $\frac{10^{6}}{10^{3}}=10^{6 - 3}$.

Step3: Simplify the exponent

$10^{6 - 3}=10^{3}$.

Answer:

$10^{3}$ (or 1000)