Slope = change in y over change in x:
Slope = (-6 6) / 2- -6) = -3/2
Equation of a line is y = Mx + b, where m is the slope and b is the y intercept.
Y = -3/2x + b
Replace y and x with one of the given points and solve for b:
6 = -3/2(-6) + b
6 = -9 + b
B = -9 + 6
B = -3
The equation of the line is y = -3/2x-3