y+3x = 6
First put the equation in slope intercept form ( y = mx+b) where m is the slope and b is the y intercept
y = -3x+6
The slope is -3
Since we want the lines to be parallel, they will have the same slope m = -3
Equation of new line
y = mx+b
y = -3x+b
We have a point on the line
(3,-4)
Substitute this point in for x and y and determine b
-4 = -3(3) +b
-4 = -9+b
Add 9 to each side to isolate b
-4+9 = -9+9+b
5 = b
y = -3x+5
The equation of a line that is parallel to 3x=6 and goes through (3,-4) is
y = -3x+5