Explanation:
3y = -x + 18
y = -1/3 x + 6 slope = -1/3 PARALLEL slope is also - 1/3
Point (3,-3) slope form of new line is then
(y+3) = -1/3 ( x -3) re-arrange
y = - 1/3x -2 <====this is slope intercept form
y + 1/3x = - 2
3y + x = - 6 <=== another form