To solve for the missing exponent in the equation:
\[ \frac{e^x}{e^{65}} = e^{38} \]
we can use the properties of exponents. Specifically, we can rewrite the left side:
\[ e^{x - 65} = e^{38} \]
Since the bases are the same (both are base \( e \)), we can set the exponents equal to each other:
\[ x - 65 = 38 \]
Now, solve for \( x \):
\[ x = 38 + 65 \] \[ x = 103 \]
Thus, the missing exponent is:
\[ \boxed{103} \]