How to lengthen line?

I am trying to lengthen the angled line to intersect the horizontal line.

I type in LENGTHEN and it asks me to select object, I select the angled line and nothing happens. Is something turned off or am I missing something here?

Select extend> right click in an open area of the drawing> left click the line you wish to extend. The line will extend to the next line.

thanks, worked great!