\[\boxed{\text{5.\ 5}}\]
\[\textbf{а)} - a + (m - n) = - a + m - n\]
\[\textbf{б)}\ c + ( - a - b) = c - a - b\]
\[\textbf{в)}\ a - (b - k - n) =\]
\[= a - b + k + n\]
\[\textbf{г)} - (a - b + c) = - a + b - c\]
\[\textbf{д)}\ (m - n) - (p - k) =\]
\[= m - n - p + k\]
\[\textbf{е)} - (a + b) + ( - c + d) =\]
\[= - a - b - c + d\ \]