The little girl is not tall enough to reach the book on the shelf(改为同义句）
the girl is(too shot ) to reach the book on the shelf.
( 楼主是不是给多了一个空?因为not adj.+enough to do sth = too +adj.+ to do sth )
也可以改为从句：
The girl is ( so short that she can't )reach the book on the shelf .
加油!不明白再问!