1. The problem asks for the coordinates of point K' after a reflection across the x-axis. 2. Reflection across the x-axis changes the y-coordinate of a point to its opposite, while the x-coordinate remains the same. 3. The formula for reflection across the x-axis is: $$ (x, y) \to (x, -y) $$ 4. Given point K has coordinates $(-2, 3)$ (since K' is at $(-2, -3)$ after reflection, original y must be positive 3). 5. Applying the reflection formula: $$ (-2, 3) \to (-2, -3) $$ 6. Therefore, the coordinates of point K' after reflection across the x-axis are $\boxed{(-2, -3)}$.