\[\boxed{\mathbf{1.}}\]
\[\textbf{а)}\]
\[\textbf{б)}\ \]
\[\boxed{\mathbf{2.}}\]
\[M \cap K = \left\{ 5 \right\};\]
\[M \cup K = \left\{ 1;3;5;6;7 \right\}.\]
\[\boxed{\mathbf{3.}}\]
\[\textbf{а)}\ 1)\ 50\ :5 = 10\ (лимонов) -\]
\[в\ одном\ пакете.\]
\[2)\ 10 \cdot 3 = 30\ (лимонов) -\]
\[в\ трех\ таких\ пакетах.\]
\[Ответ:30\ лимонов.\]
\[\textbf{б)}\ 1)\ 21\ :7 = 3\ (м) - ткани\ \]
\[надо\ на\ одно\ платье.\]
\[2)\ 42\ :2 = 21\ (платье) -\]
\[получится\ из\ 42\ м\ ткани.\]
\[Ответ:21\ платье.\]
\[\boxed{\mathbf{4.}}\]
\[90 \cdot 6 = 540\]
\[8 \cdot 15 = 120\]
\[240 \cdot 3 = 720\]
\[48\ :2 = 24\]
\[60\ :5 = 12\]
\[320\ :8 = 40\]
\[96\ :16 = 6\]
\[270\ :90 = 3\]
\[850\ :17 = 50\]
\[\boxed{\mathbf{5.}}\]
\[\textbf{а)}\ 84\ :9 = 9\ (ост.\ 3)\]
\[Проверка:\]
\[9 \cdot 9 + 3 = 81 + 3 = 84.\]
\[\textbf{б)}\ 50\ :12 = 4\ (ост.\ 2)\]
\[Проверка:\]
\[4 \cdot 12 + 2 = 48 + 2 = 50.\]
\[\boxed{\mathbf{6.}}\]
\[(7 \cdot 5)\ :35 \cdot 1 + (4 \cdot 0 + 20)\ :5 - 0 \cdot 36\ :2 =\]
\[= 35\ :35 + 20\ :5 - 0 =\]
\[= 1 + 4 = 5\]
\[\boxed{\mathbf{7.}}\]
\[\boxed{\mathbf{8.}}\]
\[\textbf{а)}\]
\[\textbf{б)}\ \]