#### Answer

The slope is undefined, which means that the line is vertical.

#### Work Step by Step

To find the slope of the line, we use the following formula:
$$m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$$
We use the given values to plug into this formula:
$$m = \frac{3 - (-1)}{6 - 6}$$
Simplify:
$$m = \frac{4}{0}$$
The slope is undefined, which means that the line is vertical.