Can anyone help me about two questions about coupled-line ?

I am not good at coupled-line theory. So can anyone help me to understand the following questions?

1) how to derive the equations 2a and 2b from 1a and 1b in this paper?

2) how to derive the even mode and odd mode circuits in Fig 7a and 7b from Fig 6?

Can't anyong do me this favor? Now I understand the question 2, but the first one is still puzzle me .

Hi
I think this is help