Question

How do you find the slope given `x = -3`?

Answer 1

The slope is indeterminate.

Explanation:

Your line is perfectly vertical. Every time you choose a value for `y` the value of `x` is ALWAYS `-3`.
From the definition of slope you have:
Slope`=(Deltay)/(Deltax)`
Let us choose two values of `y`:
`y=5 and y=10` the corresponding `x` will be `-3 and -3` so:
Slope`=(10-5)/(-3+3)=5/0` that cannot be evaluated.
Your slope is indeterminate.