Dividing the auxiliary line near coordinates (40, 0)

Choose Geometry->Edit->Divide->Lines->Near point. This option will divide the line at the point on the line closest to the coordinates entered.
Select from Mouse Menu: Contextual->No Join Ctrl-a.
Enter the coordinates of the point that will divide the line. In this example, the coordinates are (40, 0). On dividing the line, a new point (entity) has been created.
Select the line that is to be divided by clicking on it.
Press ESC to indicate that the process of dividing the line is finished. Press ESC again to finish the dividing function.

GiD user manual