line: 3x + y = s
y = s - 3x
To two lines be parallel both angular coeficients need to be equal
In y = s - 3x our angular coeficient is -3
y = ax + b where a is angular and b is linear
Now we have the equation
(y - yo) = m.(x - xo)
(y - (-4)) = -3.(x - (-1))
y + 4 = -3.(x + 1)
y + 4 = -3x - 3
y = -3x - 3 - 4
y = -3x - 7 is parallel to y = -3x + s