\[Страница\ 25.\]
\[\boxed{\mathbf{3}.}\]
\[107 < 108 < 109\]
\[999 < 1000 < 1001\]
\[3499 < 3500 < 3501\]
\[9\ 999 < 10\ 000 < 10\ 001\]
\[17\ 899 < 17\ 900 < 17\ 901\]
\[9\ 998 < 9\ 999 < 10\ 000\]
\[99\ 998 < 99\ 999 < 10\ 000\]
\[\boxed{\mathbf{4}.}\]
\[\textbf{а)}\ В\ порядке\ возрастания:\]
\[12,\ 258,\ 400,\ 893,\ 964,\ 996,\ 1891.\]
\[\textbf{б)}\ В\ порядке\ убывания:\]
\[1891,\ 996,\ 964,\ 893,\ 400,\ 258,\ 12.\]
\[\boxed{\mathbf{5}.}\]
\[391 < 392 < 393\]
\[2058 < 2063 < 2106\]
\[28\ 006 < 28\ 106 < 28\ 205\]
\[923\ 401 < 924\ 142 < 924\ 302\]
\[\boxed{\mathbf{6}.}\]
\[\textbf{а)}\ 50 < 57 < 60\]
\[\textbf{б)}\ 10 < 17 < 20\]
\[\textbf{в)}\ 80 < 82 < 90\]
\[\textbf{г)}\ 350 < 357 < 360\]
\[\textbf{д)}\ 180 < 181 < 190\]
\[\textbf{е)}\ 730 < 735 < 740\]
\[\boxed{\mathbf{7}.}\]
\[411 - нужное\ нам\ число.\]
\[\textbf{а)}\ 4,\ 1,\ 1;\]
\[\textbf{б)}\ 4,\ 1,\ 1\ или\ 2,\ 2,\ 1\]
\[\textbf{в)}\ 411.\]
\[Ответ:411.\]