1. **State the problem:** Simplify the expression $-6\left(\frac{4}{5}\right)$.\n\n2. **Recall the rule:** Multiplying a whole number by a fraction means multiplying the numerator by the whole number and keeping the denominator the same.\n\n3. **Apply the multiplication:** $$-6 \times \frac{4}{5} = \frac{-6 \times 4}{5}$$\n\n4. **Calculate the numerator:** $$\frac{-24}{5}$$\n\n5. **Final answer:** The simplified form of $-6\left(\frac{4}{5}\right)$ is $$\boxed{-\frac{24}{5}}$$ or as a decimal, $-4.8$.