How to pick the intersection point of the extension lines of these two lines, as shown in the figure

1. Enter the L command, while holding down shift and the right mouse button, as shown in the following image, select the intersection point with the left mouse button.

2. Place the cursor on one of the lines and a prompt for capturing symbols will appear. Click the left mouse button

3. Place the cursor on another line and then you will get the intersection point of the extension line as shown in the following figure