\[\boxed{\mathbf{Страница\ 20.\ }\mathbf{Еуроки\ - \ ДЗ\ без\ мороки}}\]
\[\boxed{\mathbf{1.\ }}\]
\[\mathbf{1.}\]
\[\mathbf{2.}\]
\[\mathbf{3.}\]
\[\mathbf{а)\ x + a\ :b}\]
\[\mathbf{б)\ }\left( \mathbf{c - d} \right)\mathbf{\cdot (m + n)\ }\]
\[\mathbf{4.}\]
\[A = \left\{ 1;2;3;4;6;12 \right\};\ \ \ \ \ \]
\[B = \left\{ 1;3;5;15 \right\}\]
\[A \cap B = \left\{ 1;3 \right\}\]
\[A \cup B = \left\{ 1;2;3;4;5;6;12;15 \right\}.\]
\[\boxed{\mathbf{2.\ }}\]
\[\mathbf{1.}\]