Помогите!!! Даю 20 баллов

1) (-3,9+3,9)+(4,7-4,7)+8,6=8,6
2)
$4 \frac{3}{8} + 5 \frac{1}{8} - 3 \frac{3}{7} - 9 \frac{1}{2} = \\ = 9 \frac{4}{8} - 3 \frac{3}{7} - 9 \frac{1}{2} = \\ = 9 \frac{1}{2} - 9 \frac{1}{2} - 3 \frac{3}{7} = - 3 \frac{3}{7}$
3)
$(4 \frac{9}{14} - 3 \frac{3}{14} + 1 \frac{1}{14} ) - \\ - ( \frac{5}{12} + 3 \frac{1}{12} ) = \\ (1 \frac{6}{14} + 1 \frac{1}{14} ) - 3 \frac{6}{12} = \\ = 2 \frac{7}{14} - 3 \frac{1}{2} = 2 \frac{1}{2} - 3 \frac{1}{2} = - 1$
4)
$3 \frac{1}{3} - \frac{8}{10} - 2 \frac{3}{4} + 2 \frac{5}{10} + \\ + \frac{3}{10} + 1 \frac{7}{12} = \\ = (3 \frac{1}{3} - 2 \frac{3}{4} + 1 \frac{7}{12} ) - \\ - ( \frac{8}{10} - \frac{25}{10} - \frac{3}{10} )= \\ = (\frac{10}{3} - \frac{11}{4} + \frac{19}{12} ) - \frac{20}{10} = \\ = \frac{40 - 33 + 19}{12} - 2 = \frac{26}{12} - 2 = \\ = 2 \frac{2}{12} - 2 = \frac{1}{6}$