Ok, i dont understand how they calculate the voltage. how are they getting the Vx? How do i read the circuit to know when to subtract, and add voltages? Also for Voc why do they add them together ?

Look please at picture

 

Can you upload that pdf or supply a link for it, your screen shot isn't sufficient

 

Now, u will understand the soln..
I've explained every step.

 

Sorry
not able to upload the soln.
Tell me how u did it for ur scanned docu.