\[\boxed{\text{99.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[180\ :20 = 180\ :(10 \cdot 2) =\]
\[= (180\ :10)\ :2 = 18\ :2 = 9.\]
\[1\ 800\ :200 =\]
\[= 1\ 800\ :(2 \cdot 100) =\]
\[= (1\ 800\ :100)\ :2 = 18\ :2 = 9.\]
\[450\ :50 = 450\ :(5 \cdot 10) =\]
\[= (450\ :10)\ :5 = 45\ :5 = 9.\]
\[4\ 500\ :500 =\]
\[= 4\ 500\ :(5 \cdot 100) =\]
\[= (4\ 500\ :100)\ :5 = 45\ :5 =\]
\[= 9.\]
\[= 400\ 000 - 35\ 100\ :100 =\]
\[= 400\ 000 - 351 = 399\ 649.\]
\[= 38\ 000 + 32\ 132 = 70\ 132.\]