Can you give us any hints about the encoding? You gave us one for Challenge 1. I’d love to know what to do with the minus signs and parentheses. Do we just evaluate expressions like 68-(77-53)?

EDIT: What I’d like to know most is what the book is for.

EDIT 2: Is the reference periodically updated, like Britannica or Worldbook? Would it spoil the whole thing if you simply told us what reference guide we need?