You need a line with this equation:
Where m is the slope and b is the intercept.
We know that it has to be perpendicular to
Two lines are perpendicular if their slopes are the opposite and reciprocal of each other. Therefore we have that the slope m has to be 2. For now we have:
To find the intercept we use the given point Q(6,3). If we replace these values into the equation above, we can clear b:
Now we have the full equation of the line: