Find the value of k so that the line passing through the given points has slope m. write an equation of the line in point-slope form.
(k, 4k), (k+2,3k), m = -1

You can find the value of k by using the slope formula, m = , where m is the slope and , , , and  are coordinate pairs on the line.

 m =   Plug in the values
 -1 =   Subtract 3k and 4k
 -1 =   Subtract k and k
 -1 =   Multiply both sides by 2
-2 = -k   Divide both sides by -1
 2 = k

Now, replace two with k in the coordinates to figure out the actual numbers.
   (k, 4k) and (k + 2, 3k)   Plug in 2
(2, 4(2)) and (2 + 2, 3(2))   Simplify
    (2, 8) and (4, 6)

Now, choose one of those coordinates and plug it into the point-slope equation (). I'll use (2, 8).

  Plug in slope and the coordinate
y - 8 = -1 (x - 2)

The correct answer is c