Answer
$x \approx 0.439$
Work Step by Step
Take the natural log of both sides to get $$\ln e^{-5x} = \ln 9$$ Since $\ln a^b=b \ln a$, the equation becomes $$-5x \ln e = -5x = \ln 9$$ Divide both sides by $-5$ to get $$x=\frac{\ln 9}{-5} \approx-0.439$$
