intercept

Hello, Could someone kindly explain, in detail, how the intercept angles match the RMI indications as shown in the attached pdf? I dont understand it at all. thank you. kindly see attached pdf.

So I just started instrument training with a new instructor (different from PPL) and we were attempting to intercept a radial for a VOR. The instructor was using some method I had never heard of before and I can't seem to remember how it worked. It went something like this--add 100 degrees...