Answer: slope is -1/3
a parallel line answer is below
Explanation:
3x+9y=12 can be automatically rewritten as 9y=-3x+12 but the proper form is y= (−1/3)x +(4/3)
to find a parallel line to another slope, you must keep the slope and change the y intercept.
so for example:
y= -1/3x + 4 would follow this rule
but really you can change the y intercept to anything reasonable