There are two fifths more story books than literature books. B 420× two fifths.
3. Story books are equivalent to two-fifths of literary books (1+two-fifths).
4. Story books are two-fifths less than literature books, and the D is 420× (1-two-fifths).
Literature books are equivalent to two-fifths of story books.
6. Literary books are two fifths less than story books (f 420×( 1+ two fifths).
1c，2f，3b，4d，5e，6a。