-6
We assume "initial value" means the y-intercept is (0, 6). The rate of change is the "rise" divided by the "run" between the two points.
rise = -6 -6 = -12 . . . . difference of y-values
run = 2 -0 = 2 . . . . . . difference of corresponding x-values
rate of change = rise/run = -12/2 = -6
The rate of change of this line is -6.
