\[10\ :\left( 2\frac{12}{17} + 1\frac{5}{17} \right) - \left( 3\frac{4}{5} + 1\frac{3}{5} \right)\ :6 =\]
\[= 10\ :3\frac{17}{17} - (3,8 + 1,6)\ :6 =\]
\[= 10\ :4 - 5,4\ :6 = 2,5 - 0,9 = 1,6\]