\[\boxed{\mathbf{4.55.}\mathbf{ОК\ ГДЗ - домашка\ на\ }5}\]
\[\textbf{а)}\ 39\ :3 = 13 + 37 = 50\ :5 =\]
\[= 10 \cdot 11 = 110\ :55 = 2\]
\[\textbf{б)}\ 28\ :2 = 14 + 40 = 54\ :3 =\]
\[= 18 \cdot 5 = 90\ :15 = 6\]
\[\textbf{в)}\ 72\ :3 = 24\ :12 = 2 + 44 =\]
\[= 46\ :23 = 2 \cdot 35 = 70\]
\[\textbf{г)}\ 80\ :20 = 4 \cdot 15 = 60\ :30 =\]
\[= 2 + 19 = 21 \cdot 5 = 105\]
\[\textbf{д)}\ 100\ :10 = 10 \cdot 7 = 70\ :14 =\]
\[= 5 \cdot 25 = 125 - 75 = 50\]