\[\boxed{\mathbf{Стр.\ }\mathbf{12.}}\]
\[\boxed{\mathbf{1}.}\]
\[\boxed{\mathbf{2}.}\]
\[43 + 8 = 43 + 7 + 1 = 51\]
\[51 - 8 = 51 - 1 - 7 = 43\]
\[75 - 9 = 75 - 5 - 4 = 66\]
\[66 + 9 = 66 + 4 + 5 = 75\]
\[\boxed{\mathbf{3}.}\]
\[(18 + 7) - 20 = 25 - 20 =\]
\[= 5\ (лодок) - осталось\ у\ \]
\[пристани.\]
\[Ответ:5\ лодок.\]
\[\boxed{\mathbf{4}.}\]
\[9 + 4 = 13\ (лодок) - ушло\ в\ \]
\[море.\]
\[Ответ:13\ лодок.\]
\[\boxed{\mathbf{5}.}\]
\[37 + 8 = 45\]
\[56 - 9 = 47\]
\[60 - 32 = 28\]
\[80 - 47 = 33\]
\[10 = 1\ дес.\ 0\ ед.\]
\[18 = 1\ дес.\ 8\ ед.\]
\[\boxed{\mathbf{6}.}\]
\[13 - 6 + 8 = 7 + 8 = 15\]
\[14 - 9 + 6 = 5 + 6 = 11\]
\[80 - (12 - 7) = 80 - 5 = 75\]
\[90 - (14 - 8) = 90 - 6 = 84\]
\[32 - 7 = 25\]
\[45 - 9 = 36\]
\[\boxed{\mathbf{Вопрос}.}\]
\[\boxed{\mathbf{Задание\ на\ полях}.\ Какая\ фигура\ лишняя?}\]
\[Лишняя\ фигура\ №2:\]
\[желтая.\]
\[Лишняя\ фигура\ №3:\]
\[из\ 5\ клеток.\]