Storybook: 1680×30%=504 (Ben)
Comics: 1680×25%=420 (Ben)
Science and technology tree: 1680×45%=756 (Ben)
(2)
Story books are less than science books: 756-504=252 (this)
There are more story books than comic books: 504-420=84 (books)
(3)
The proportion of storybooks and comic books is
504 :420=6 :5