§ Задание 20
\[\boxed{\mathbf{20.}}\]
\[30 + 1 = 31\]
\[30 + 10 = 40\]
\[50 + 1 = 51\]
\[50 + 10 = 60\]
\[70 + 1 = 71\]
\[70 + 10 = 80\]
\[90 + 1 = 91\]
\[90 + 10 = 100\]
\[\boxed{\mathbf{20.}}\]
\[30 + 1 = 31\]
\[30 + 10 = 40\]
\[50 + 1 = 51\]
\[50 + 10 = 60\]
\[70 + 1 = 71\]
\[70 + 10 = 80\]
\[90 + 1 = 91\]
\[90 + 10 = 100\]