\[\left( x^{8} \cdot x^{2} \right)\ :\left( x^{4} \cdot x^{5} \right) =\]
\[= x^{8 + 2}\ :x^{4 + 5} = x^{10}\ :x^{9} =\]
\[= x^{10 - 9} = x^{1} = x.\]