\[\boxed{\mathbf{2}\mathbf{.}}\]
\[1)\ 3 + 3 + 3 + 3 + 3 + 3 + 3 =\]
\[= 21\]
\[3 \cdot 7 = 21\]
\[2)\ 3 + 3 + 3 + 3 + 3 + 3 + 3 + 3 = 24\]
\[3 \cdot 8 = 24\]
\[3 \cdot 9 = 27\]
\[3 \cdot 10 = 30\]