1. **State the problem:** Simplify the expression $$\frac{20x^{-3}c}{4x^{4}-5}$$. 2. **Recall the rules:** When simplifying expressions with exponents, remember that $x^{-n} = \frac{1}{x^{n}}$. 3. **Rewrite the expression:** The numerator is $20x^{-3}c = 20c \cdot x^{-3} = \frac{20c}{x^{3}}$. 4. **Substitute back:** The expression becomes $$\frac{\frac{20c}{x^{3}}}{4x^{4}-5} = \frac{20c}{x^{3}(4x^{4}-5)}$$. 5. **Final simplified form:** $$\boxed{\frac{20c}{x^{3}(4x^{4}-5)}}$$. This is the simplest form since the denominator cannot be factored further and numerator and denominator share no common factors.