Different, but the Same

You'll find that most teachers will assign readings and problems in a similar way. There are differences, but most are so small as to not mention.

• Ch, Chap, Chapter
  common abbreviations for chapter
• S, Sect, Section
  common abbreviations for section
• #, Prob, Problem
  common abbreviations for problem
• p, pp, page(s)
  common abbreviations for page or pages
• 2.1
  means (sub)section 1 of chapter/section 2
  or
  means problem 1 from chapter/section 2
  or
  means part 1 of problem 2
• 1-3
  means parts 1 thru 3 of something (problems 1 thru 3, sections 1 thru 3, chapters 1-3, etc.)
• 21-4
  means parts 21 thru 24 (the common '20' is left off the second one)
• 321-4
  means parts 321 thru 324 (the common '320' is left off the second one)
• 321-44
  means parts 321 thru 344 (the common '300' is left off the second one)
• 42-78 (evens)
  means do just the even numbered problems between 42 and 78 -- including both 42 and 78!
• 41-79 (odds)
  means do just the odd numbered problems between 41 and 79 -- including both 41 and 79!

Commas will separate similar things while semi-colons will be used to separate not-so-similar things. For instance:

    Ch1;2.1,3

Here the reading assignment is all of chapter 1 as well as sections 1 and 3 of chapter 2. On the other hand:

    Ch1,2.1,3

Now the assignment is chapter 1, section 1 of chapter 2, and chapter 3. See the difference? Well, think it over a bit and maybe it'll click in place:

    Ch1;2.1,3          vs           Ch1,2.1,3