\[\boxed{\text{5.\ 64}}\]
\[\textbf{а)}\ 3y - 3b + 7y - 5b + 7b =\]
\[= 10y - b\]
\[y = - 0,24;\ \ b = 0,04:\]
\[- 0,24 \cdot 10 - 0,04 =\]
\[= - 2,4 - 0,04 = - 2,44.\]
\[\textbf{б)} - 6,3m + 8 - 3,2m - 5 =\]
\[= - 9,5m + 3\]
\[m = - 2:\]
\[- 9,5 \cdot ( - 2) + 3 = 19 + 3 = 22.\]
\[m = - \frac{1}{8}:\]
\[- \frac{95}{10} \cdot \left( - \frac{1}{8} \right) + 3 = \frac{95}{80} + 3 =\]
\[= \frac{19}{16} + 3 = 1\frac{3}{16} + 3 = 4\frac{3}{16}.\]
\[m = - 0,4:\]
\[- 9,5 \cdot ( - 0,4) + 3 = 3,8 + 3 =\]
\[= 6,8.\]