\[\boxed{\text{83.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[240\ :(4 \cdot 10) = (240\ :10)\ :4 =\]
\[= 24\ :4 = 6.\]
\[180\ :(2 \cdot 10) = (180\ :10)\ :2 =\]
\[= 18\ :2 = 9.\]
\[540\ :(9 \cdot 10) = (540\ :10)\ :9 =\]
\[= 54\ :9 = 6.\ \]