Hello!
If a you want to find an equation of the line that is parallel to the given line, we must know that if two lines are parallel, then their slope will <em>always</em> have to be equal.
This means that the new equation must have a slope of -1/3.
Also, you would need to substitute the given point (6, 8) into the equation with the slope: -1/3 as well. Following these steps allows you to find the equation of line.
y = -1/3x + b (6, 5)
5 = -1/3(6) + b
5 = -2 + b (add 2 to both sides)
7 = b
Therefore, the equation of the line is y = -1/3x + 7.