What is an equation of the line through (-1,-4) and parallel to the line 3x+y=s

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