The expression \( x^{-3} \) can be rewritten using positive exponents. According to the rules of exponents, specifically, the rule that states \( a^{-n} = \frac{1}{a^n} \), we can express \( x^{-3} \) as:
\[ x^{-3} = \frac{1}{x^3} \]
So, the equivalent expression to \( x^{-3} \) is \( \frac{1}{x^3} \).