\[\boxed{\mathbf{972\ (962).}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ \left( 7 + ( - 20) \right) + 18 =\]
\[= 7 - 20 + 18 = 5\]
\[2)\ 7,9 + \left( 2,1 + ( - 10) \right) =\]
\[= 7,9 + 2,1 - 10 = 0\]
\[3)\ \left( 3\frac{11}{16} + \left( - 2\frac{5}{16} \right) \right) +\]
\[+ \left( 4\frac{17}{36} + \left( - 1\frac{11}{36} \right) \right) = 3\frac{11}{16} -\]
\[- 2\frac{5}{16} + 4\frac{17}{36} - 1\frac{11}{36} =\]
\[= 1\frac{6}{16} + 3\frac{6}{36} = 1\frac{3}{8} + 3\frac{1}{6} =\]
\[= 1\frac{9}{24} + 3\frac{4}{24} = 4\frac{13}{24}\]