There are two videos (probably found elsewhere in this website also) which are made to be the solution to the Week 5 homework.
The Week 5 homework was extensive. The voltage divider theory works by building on series parallel circuits.
In reviewing parallel circuits here is a narrated video powerpoint which may help. (I’ll narrate the followup powerpoint to this one in due course and add it here also)
The homework solution videos are as shown here:
and part 2: