fixed some typos

just fixed some typos also changed the width of the table 8.1 (just so there is more space for the definition and a little less for the number) the euro symbol wasn't displaying in the formula (in "Decision analysis") so changed it that it now shows the symbol in the book

requested review from @rlanzafame

assigned to @I.C.Slingerland-1

merged

mentioned in commit b1a9d425