\[\boxed{\text{5.\ 9}}\]
\[\textbf{а)}\ x - (x - z) = x - x + z = z\]
\[\textbf{б)} - (b - d) - d =\]
\[= - b + d - d = - b\]
\[\textbf{в)}\ c - (a + c) = c - a - c = - a\]
\[\textbf{г)}\ z + (y - x - z) =\]
\[= z + y - x - z = y - x\]
\[\textbf{д)}\ a + ( - b + c - d) =\]
\[= a - b + c - d\]
\[\textbf{е)} - c - (n - c + r) =\]
\[= - c - n + c - r = - n - r\ \]
\[\textbf{ж)} - (k - d) - (s + d) =\]
\[= - k + d - s - d = - k - s\]
\[\textbf{з)} - (s + d) - (z + d) =\]
\[= - s - d - z - d =\]
\[= - s - z - 2d\]
\[\textbf{и)}\ n - (c + n) - ( - c - n) =\]
\[= n - c - n + c + n = n\ \]