\[\boxed{\text{5.\ 11}}\]
\[\textbf{а)} - 14 + c - (c + 70,8) =\]
\[= - 14 + c - c - 70,8 = - 84,8\]
\[\textbf{б)}\ 2,6 - a - \left( - a + 7\frac{2}{5} \right) =\]
\[= 2,6 - a + a - 7,4 = - 4,8\]
\[\textbf{в)}\ x + a - (c + x) =\]
\[= x + a - c - x = a - c\]
\[\textbf{г)} - a + b - (b - a) =\]
\[= - a + b - b + a = 0\ \]
\[\textbf{д)} - x - a - (x + a) =\]
\[= - x - a - x - a = - 2x - 2a\]
\[\textbf{е)}\ n - c - ( - c + n - b) =\]
\[= n - c + c - n + b = b\]