1. **State the problem:** Find the midpoint of the points $A(15, 18)$ and $B(15, 18)$. 2. **Formula:** The midpoint $M$ of two points $A(x_1, y_1)$ and $B(x_2, y_2)$ is given by: $$M = \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right)$$ 3. **Apply the formula:** Here, $x_1 = 15$, $y_1 = 18$, $x_2 = 15$, and $y_2 = 18$. Substitute these values: $$M = \left( \frac{15 + 15}{2}, \frac{18 + 18}{2} \right)$$ 4. **Simplify:** $$M = \left( \frac{30}{2}, \frac{36}{2} \right)$$ 5. **Calculate:** $$M = (15, 18)$$ 6. **Interpretation:** Since both points are the same, the midpoint is the same point $A$ and $B$.