\[\boxed{\text{966\ (966).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ y = 0:\ \ \]
\[7 \cdot 0 - 3x = 21\ \]
\[- 3x = 21\ \]
\[x = - 7 \Longrightarrow \ \ ( - 7;0).\]
\[2)\ x = 0:\ \ \]
\[7y - 3 \cdot 0 = 21\]
\[7y = 21\ \]
\[y = 3 \Longrightarrow (0;3)\]