How to get LHA and Ap longitude in Eastern longitudes

[P.Rutherford]

Peter,

The final check (only really important for taking exams) is to confirm in either case that your resulting AP longitude is within 30.0' of longitude from your DR position, and if not to adjust the whole degree value of your AP by one degree while leaving the minutes and tenths alone so that it is -- just so your results will match the exam question answer.

I understand about Ap and LHA in Western longitudes and because of your excellent explanation above, about Ap and LHA in Eastern longitudes and how to get it for exams.

But, it's the Western longitudes I'm now curious about and the need to be within 30 minutes of DR λ and Ap λ to subtract (or add?) 1°.  

Can you give an example?

Thanks,

Paul