Answer:
y = -2x +4
Explanation:
It usually works well to start with the point-slope form of the equation for a line:
y = m(x -h) +k . . . . . . . a line with slope m through point (h, k)
Filling in your values, we have ...
y = -2(x -(-8)) +20
y = -2x -16 +20 . . . . . . eliminate parentheses
y = -2x +4 . . . . . . . . . . simplify