The expression \( 3\sqrt{5} \) can be rewritten using rational exponents. The cube root of a number can be expressed as that number raised to the power of \( \frac{1}{3} \).
Thus, \( 3\sqrt{5} \) can be written as:
\[ 5^{\frac{1}{3}} \]
So, the rational exponent in the equivalent expression to \( 3\sqrt{5} \) is:
\[ \frac{1}{3} \]