Answer
=7 $\times$ $10^{-3}$
Work Step by Step
You have $\frac{3.5*10^6}{5* 10^8}$.Simplify:
$\frac{3.5*10^6}{5* 10^8}$ -subtract the exponents-
$10^{6-8}$=$10^{-2}$
$\frac{3.5}{5}$ $\times$ $10^{-6}$ -divide the terms-
=7 $\times$ $10^{-3}$