Step-by-step explanation:
Let 
The slope of the line through these two points is

So the slope-intercept form of the line passing through the two points is

To find b, we use either point into our equation. Let's use (-1, -8):

Therefore, the slope-intercept form of the equation for the line is

The standard form of the equation can be written as

Let's get the data out of the problem:
Nv = 18
Ov = 12
Now, we can apply in this equation that relates the new and the old values:
i = Nv / Ov
i = 18 / 12
i = 1.5
Now, we just consider what has passed from 1, and this is 0.5, converting to percentage it is:
p = 0.5 . 100
p = 50%
The increase was 50%.
Hope it helps.
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3x-9=2x+4
3x-9+9=2x+4+9
3x=2x+13
3x-2x=2x-2x+13
x=13
Check:
3(13)-9=2(13)+4
39-9=26+4
30=30
We can’t attach imagines on here