To draw the line from a "picked" starting point try this. In your line command pick the starting point and then type in @24'<ANGLE where ANGLE is the angle you want to draw the line at. Hope this helps.
I believe you can use the front panel on the HP750C to nest the drawings. Nesting is used to place drawings side-by-side to avoid wasting media. If you have the users guide for the plotter the steps to set nesting up can be found there.