\[Страница\ 29.\]
\[\boxed{\mathbf{21.}}\]
\[26 - (14 - 8) = 26 - 6 = 20\]
\[40 - (13 + 7) = 40 - 20 = 20\]
\[35 - (13 - 9) = 35 - 4 = 31\]
\[60 - (28 + 2) = 60 - 30 = 30\]
\[100 - 8 = 92\]
\[100 - 18 = 82\]
\[\boxed{\mathbf{22.}}\]
\[1)\ \]
\[2)\ 6 \cdot 3 = 18\ (карандашей) - в\ \]
\[трех\ таких\ коробках.\]
\[Ответ:18\ карандашей.\]
\[\boxed{\mathbf{23.}}\]