Question

What is the slope of the line represented by the equation x = -9

Answer 1

Slope is the change in y over the change in x.
Does x ever change on this line?

Answer 2

keep in mind that x = -9

y = 5, x = -9
y = -5, x = -9
y = 100, x = -9
y = -100, x = -9
y = -1000, x = -9
y = 1000, x = -9

so slope = rise/run
what's the rise?
what's the run?