Answer
$3.0\times10^{-21}$
Work Step by Step
Using the laws of exponents and the concepts of scientific notation, the given expression, $
\dfrac{7.5\times10^{-9}}{2.5\times10^{12}}
$, simplifies to
\begin{array}{l}
(7.5\div2.5)\times10^{-9-12}
\\\\=
3.0\times10^{-21}
.\end{array}