\[\boxed{\text{6.357.}}\]
\[\textbf{а)}\ 19,44\ :7,2 = 194,4\ :72 = 2,7\ \]
\[\textbf{б)}\ 1,972\ :5,8 = 19,72\ :58 =\]
\[= 0,34\ \]
\[\textbf{в)}\ 41,666\ :8,3 = 416,66\ :83 =\]
\[= 5,02\ \]
\[\textbf{г)}\ 1,8315\ :4,5 = 18,315\ :45 =\]
\[= 0,407\ \]
\[\textbf{д)}\ 213,9\ :9,3 = 2139\ :93 = 23\ \]
\[\textbf{е)}\ 0,0825\ :0,33 = 8,25\ :33 =\]
\[= 0,25\ \]
\[\textbf{ж)}\ 0,03472\ :0,028 =\]
\[= 34,72\ :28 = 1,24\ \]
\[\textbf{з)}\ 15,39\ :4,05 = 1539\ :405 =\]
\[= 3,8\ \]
\[\textbf{и)}\ 86,496\ :21,2 =\]
\[= 864,96\ :212 = 4,08\ \]