#### Answer

midpoint = $(-6, -2)$

#### Work Step by Step

In this problem, we need to use the midpoint formula.
The midpoint can be found using the following formula:
midpoint = $(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2})$, where $(x_1, y_1)$ and $(x_2, y_2)$ are the endpoints of the line segment.
The points we are given are $M (6, -11)$ and $N (-18, 7)$. Let's plug these points into the formula:
midpoint = $(\frac{6 + (-18)}{2}, \frac{-11 + 7}{2})$
Use addition to simplify:
midpoint = $(\frac{-12}{2}, \frac{-4}{2})$
Divide to simplify:
midpoint = $(-6, -2)$