Certain operations on linked list elements - How to?

Hi, all!

First, I’ve used search on this forum for my problem and found some very good articles about linked list, but nothing that can help me.

So, is it possible to write function in C for adding two adjoining elements of the list?
And to start that adding from second element of the list, so the first one stays the same?
Here is what I need to do:
If elements of the list are: a5, a4,…a1, I need to get the following elements:
b4=a5, b3=xb4+a4,…, b1=xb2+a2, b0=x*b1+a1, where x is integer value argument of the function.