Please check the figure attached.
The equations given could be interpreted as:
y= -3x+12
y= -3x+4
With this kind of pattern, we don't have to do any algebra since by observation, this means that the two lines are parallel because they have the same slope. (the slope is the coefficient on x).
Looking at the y-intercepts:
|12-4|=8
Therefore, the distance between them is 8 units.
