The axis of symmetry is found within the set of parenthesis with the x. If our h value of the vertex is -4, then the axis of symmetry is x = -4. D is that choice. Cannot graph it here, but your vertex is sitting at (-4, 4), it's an upside down parabola, and some other points on this graph are (-5, 0), (-3, 0), (-6, -12), (-2, -12). You could graph it using those points and the vertex without a problem, I'm sure.
Let's start by moving all like terms to their own sides:
-18 = -3x + 6
3x = 6 + 18
3x = 24
x = 8
You would have to use this equation : y2-y1/x2-x1 = slope
So it would be -13 +3/6-2= -10/4
Simplify it and you get : -5/2
Slope is -5/2
You add 1 to the numerator each time
Nothing changes if you don't add anything.
Example:
10+10=20
20+0=20
nothing changes.