1. **State the problem:** Given two functions $f(x) = 5 - x$ and $g(x) = x^3$, find the composition $fg(x)$, which means $f(g(x))$. 2. **Recall the composition formula:** The composition $fg(x)$ is defined as $f(g(x))$, which means you substitute $g(x)$ into $f$. 3. **Substitute $g(x)$ into $f$:** Since $g(x) = x^3$, then $$fg(x) = f(g(x)) = f(x^3) = 5 - x^3.$$ 4. **Final answer:** The composition function is $$fg(x) = 5 - x^3.$$