We have a line passing through 3 points. We can use the first
two points to find the equation of the line.
(6,3), (8,4)
slope m = (4-3)/(8-6) = 1/2
We can use the point slope form y-y1 = m(x-x1) or
the slope intercept form y = mx + b
to find the equation of the line.
Let's take the point (6,3) and use y = mx + b to find b
y = 3, x = 6, m = 1/2
3 = (1/2)(6) + b
3 = 3 + b
0 = b
The equation of our line is y = (1/2)x
We have a line of equation y = (1/2)x going through point (n,-2)
Plugging in we have: -2 = (1/2)n
2(-2) = n
-4 = n
Your answer is n = -4
NOTE: looking at the 3 points as given initially: (6,3), (8,4), (n,-2)
We can see that 3 = (1/2)6 and 4 = (1/2)8 so -2 = (1/2)n makes sense
Hope this helps you :)