-1 - ⅓x = y is the answer because of this:
Point-Slope Formula FIRST [GIVEN BOTH SLOPE AND A POINT]: y + 3 = -⅓(x - 6) ["+" was inserted because of (-(-3)) = 3]
Distributive Property: y + 3 = ⅓x + 2
Final Result [deduct 3 from both sides of the equation]: -1 - ⅓x = y (OR y = ⅓x - 1)
You get it?
