I have been able to figure out E5.6 but for the life of me I can't figure out E5.7. Can someone please help explain how they get to this answer using Nortons theorem?

 

It makes no sense.

Unless I am missing something (always possible), they are asking you to find the same voltage in the same circuit in both problems, just asking you to find it using a different method. So the answer should be the same in both cases.

And I see no reason to remove the 4kΩ resistor. If you leave it in you get a Norton equivalent circuit that is compatible with the Thevenin circuit and that yields the same answer as E5.6.

For anything more, you need to show your work.

 

Looks like you stumble upon a typo that is not yet updated in their errata.

http://bcs.wiley.com/he-bcs/Books?action=resource&bcsId=6094&itemId=0470633220&resourceId=27157