Answer
$\frac{s^{12}}{t^{20}}$
Work Step by Step
According to the power rule for exponents, $(a^{m})^{n}=a^{mn}$ (where $m$ and $n$ are integers and $a$ is a real number).
Therefore, $(\frac{-s^{3}}{t^{5}})^{4}=(\frac{-1\times s^{3}}{t^{5}})^{4}=\frac{(-1)^{1\times4}s^{3\times4}}{t^{5\times4}}=\frac{(-1)^{4}s^{12}}{t^{20}}=\frac{s^{12}}{t^{20}}$.