We know that two lines are parallel if they have the same slope, so we can you the equation y = 3x+b because the lines are parallel and 3 represents the slope.
y = 3x+b (6,8)
We can substitute the points in the equation
8 = 3*6 + b
I put 8 in y slot because 8 is the point on the y-axis and I put 6 in the x slot because it is the point on the x-axis
8 = 3*6 + b
8 = 18+b
-18 -18
-10 = b
The equation is
y = 3x -18