\[\boxed{\text{5.\ 61}}\]
\[\textbf{а)}\ 20x + y - 20y - x =\]
\[= 19x - 19y\]
\[\textbf{б)} - 4b + 5a + 4b + 5a = 10a\]
\[\textbf{в)} - 9c + 4,8n + 4c + 4n =\]
\[= - 5c + 8,8n\]
\[\textbf{г)}\ 5,3m + 4,7m - 7,1x + 25x =\]
\[= 10m + 17,9x\]
\[\textbf{д)}\ \frac{3}{4}z - \frac{4}{9}y - \frac{7}{22}z + \frac{2}{3}y =\]
\[= \frac{33}{44}z - \frac{14}{44}z - \frac{4}{9}y + \frac{6}{9}y =\]
\[= \frac{19}{44}z + \frac{2}{9}y\]
\[\textbf{е)} - 9c + 8c - y + 13 =\]
\[= - c - y + 13\ \]
\[\textbf{ж)}\ 42a - 42 + 50 + 4a =\]
\[= 46a + 8\]
\[\textbf{з)} - s + 2r + 1,4s - 2,7r =\]
\[= 0,4s - 0,7r\]
\[\textbf{и)} - 24b + 12d + 2,4b - 1,2d =\]
\[= - 21,6b + 10,8d\]
\[к)\ \frac{1}{2}a - \frac{2}{7}c - 0,4a - \frac{1}{7}c =\]
\[= 0,5a - 0,4a - \frac{3}{7}c =\]
\[= 0,1a - \frac{3}{7}c\]