Answer
$2.5\times10^1$
Work Step by Step
Divide the top by the bottom, and divide the exponents by subtracting them. Then move the decimal point to after the ones place and write in the appropriate exponent after the move.
$\frac{5\times10^{-6}}{20\times10^{-8}}$
$0.25\times10^{(-6-(-8))}$
$0.25\times10^{2}$
$2.5\times10^1$