\[\boxed{\mathbf{1.}\mathbf{66}\mathbf{.\ ОК\ ГДЗ - домашка\ на\ }5}\]
\[\textbf{а)}\ 0,5 \cdot 4 = 2;\ \]
\[2\ :0,1 = 20;\ \]
\[20 - 0,8 = 19,2;\ \]
\[19,2\ :30 = 0,64.\ \]
\[\textbf{б)}\ 7,2\ :0,1 = 72;\ \]
\[72\ :7,2 = 10;\ \]
\[10 \cdot 0,36 = 3,6;\ \]
\[3,6 + 0,7 = 4,3.\]
\[\textbf{в)}\ 57 \cdot 0,1 = 5,7;\ \]
\[5,7\ :3 = 1,9;\ \]
\[1,9 + 4,4 = 6,3;\ \]
\[6,3\ :0,9 = 7.\ \]
\[\textbf{г)}\ 4,4\ :11 = 0,4;\ \]
\[0,4\ :0,1 = 4;\ \]
\[4 \cdot 0,25 = 1;\ \]
\[1\ :20 = 0,05.\ \ \ \ \]