\[Стр.\ 49.\]
\[\boxed{\mathbf{8.}}\]
\[\textbf{в)}\ 9\frac{1}{4} + \left( - 8\frac{3}{7} \right) + 2\frac{3}{4} + \left( - 7\frac{4}{7} \right) =\]
\[= 12 + ( - 16) = - 4\]
\[\textbf{г)} - 4\frac{2}{7} + 3\frac{3}{14} - 1\frac{1}{2} + 5\frac{1}{2} =\]
\[= 8\frac{10}{14} + \left( - 5\frac{11}{14} \right) = 2\frac{13}{14}\]
\[\boxed{\mathbf{9.}}\]
\[\textbf{а)}\ (58 + 24) - 65 = - 34 - 65 =\]
\[= - 31\]
\[\textbf{б)} - 70 + (32 + 19) =\]
\[= - 70 + 51 = - 19\]
\[\textbf{в)} - 7 - ( - 9 - 40) =\]
\[= - 7 - ( - 49) = 42\]
\[\textbf{г)}\ 4,2 - ( - 2,9 + 3,6) =\]
\[= 4,2 - 0,7 = 3,5\]
\[\textbf{д)}\ ( - 6,5 + 50) - 0,5 =\]
\[= 43,5 - 0,5 = 43\]
\[\textbf{е)}\ (17,8 - 35) + 40 =\]
\[= - 17,2 + 40 = 22,8\]
\[\textbf{ж)}\ \left( - 2\frac{1}{3} - 7\frac{1}{3} \right) + 2,3 =\]
\[= - 9\frac{2}{3} + 2\frac{3}{10} = - 9\frac{20}{30} + 2\frac{9}{30} =\]
\[= - 7\frac{11}{30}\]
\[\textbf{з)} - 5\frac{2}{5} - \left( - 7\frac{1}{4} - 6\frac{3}{8} \right) =\]
\[= - 5\frac{2}{5} - \left( - 7\frac{2}{8} - 6\frac{3}{8} \right) =\]
\[= - 5\frac{2}{5} + 13\frac{5}{8} =\]
\[= - 5\frac{16}{40} + 13\frac{25}{40} = 8\frac{9}{40}\]