Answer:
The answer is - 4
Explanation:
Equation of a line is y = mx + c
where
m is the slope
c is the y intercept
12x + 3y = 15
Express it in the form y = mx + c
3y = -12x + 15
Divide all terms by 3
y = - 4x + 5
From the equation m = - 4
Since the lines are parallel their slope are also the same
So the slope of the parallel line is also - 4
Hope this helps you