Answer
$$
\left(e^{3}\right)^{-2 x} =e^{-x+5}
$$
So, the solution of the given equation is
$$
x=-1.
$$
Work Step by Step
$$
\left(e^{3}\right)^{-2 x} =e^{-x+5}
$$
Since the bases is the same, then we have
$$
\begin{aligned}\left(e^{3}\right)^{-2 x} &=e^{-x+5} \\ e^{-6 x} &=e^{-x+5} \\-6 x &=-x+5 \\-5 x &=5 \\ x &=-1 \end{aligned}
$$
So, the solution of the given equation is
$$
x=-1.
$$