Sec. 7, 4.1-4.2 due January 25

The most difficult part was understanding the notation.  I think I've a decent grasp of it, but stressing it in class would go a long way to allowing me to fully understand it.  I'm still struggling to see n | (a-b) as "a is congruent to b modulo n.  Aside from this it seems a fairly straight forward extension of the sections from the previous class period.