\[\boxed{\text{4.\ 285}}\]
\[\textbf{а)}\ n + n + n + n = 4 \cdot n\]
\[\textbf{б)} - c - c - c - c = - c \cdot 4\]
\[\textbf{в)} - 4a - 4a - 4a - 4a =\]
\[= - 4a \cdot 4\]
\[\textbf{г)}\ 3z + 3z + 3z + 3z + 3z + 3z =\]
\[= 3z \cdot 6\]