The mean kinetic energy for gas molecules
$E=\frac{3}{2}KT$
$\Rightarrow E \propto T $
So, $\frac{E_{1}}{E_{2}}=\frac{T_{1}}{T_{2}} \ldots\left(i\right)$
According to question both the gases are at the same temperature $T$
So, $\frac{E_{1}}{E_{2}}=\frac{T}{T}=\frac{1}{1}$
$\Rightarrow E_{1} : E_{2}$
$=1:1$