Help me on this math question

9.

10.

Exaplanation:

Please refer to my Answer from this question to know more about the slope of a line:

In graph 9, we can see a line that is perfectly horizontal. Graphs of lines that are horizontal has a slope of, .

If you want we can still solve for the slope of the line in graph 9, without acknowledging that the line is horizontal.

In graph 9, we can see that the points, and , is on the line. These can be our points and .

In graph 10, we can see that the points, and , is on the line. These can be our points and .