1. **State the problem:** Find the slope of the line passing through points $D(-1, 9)$ and $G(4, 9)$. 2. **Formula for slope:** The slope $m$ between two points $(x_1, y_1)$ and $(x_2, y_2)$ is given by: $$m = \frac{y_2 - y_1}{x_2 - x_1}$$ 3. **Apply the formula:** Substitute $D(-1, 9)$ as $(x_1, y_1)$ and $G(4, 9)$ as $(x_2, y_2)$: $$m = \frac{9 - 9}{4 - (-1)} = \frac{0}{5}$$ 4. **Simplify:** $$m = 0$$ 5. **Interpretation:** A slope of zero means the line is horizontal. **Final answer:** The slope of the line passing through points $D$ and $G$ is $0$.