The general form of the equation of the line is:
where m is the slope of the line and b the y-intersect. Lines with the same slope are considered parallels between them.
You have a line which is parallel to the line y=-1/7x -1, and tha passes trough the point (2,-1).
The slope of the searched line is m=-1/7. In order to find theequation of the line, you use the following formula for the slope of a line:
where (x0,y0) is one of the points of the line. In this case you consider this point is (2,-1). You replace these values of the point and the values of the slope into the formula for the slope and you proceed as follow:
The previous equation, is the equation of the searched line.