6. Вычислите: 1) 2/8 + 5/8; 2) 7/12 − 3/8; 3) 11/18 − 5/8; 4) 8/35 + 3/10; 5) 8/15 − 4/9; 6) 4/15 + 7/12; 7) 11/48 − 5/38; 8) 4/5 − 2/3 + 4/15; 9) 7/8 + 11/12 − 5/6.

Приводим дроби к общему знаменателю, затем выполняем сложение или вычитание числителей.

1. \(\frac{2}{8}+\frac{5}{8}=\frac{7}{8}\).
2. \(\frac{7}{12}-\frac{3}{8}=\frac{14}{24}-\frac{9}{24}=\frac{5}{24}\).
3. \(\frac{11}{18}-\frac{5}{8}=\frac{44}{72}-\frac{45}{72}=-\frac{1}{72}\).
4. \(\frac{8}{35}+\frac{3}{10}=\frac{16}{70}+\frac{21}{70}=\frac{37}{70}\).
5. \(\frac{8}{15}-\frac{4}{9}=\frac{24}{45}-\frac{20}{45}=\frac{4}{45}\).
6. \(\frac{4}{15}+\frac{7}{12}=\frac{16}{60}+\frac{35}{60}=\frac{51}{60}=\frac{17}{20}\).
7. \(\frac{11}{48}-\frac{5}{38}=\frac{418}{1824}-\frac{240}{1824}=\frac{178}{1824}=\frac{89}{912}\).
8. \(\frac{4}{5}-\frac{2}{3}+\frac{4}{15}=\frac{12}{15}-\frac{10}{15}+\frac{4}{15}=\frac{6}{15}=\frac{2}{5}\).
9. \(\frac{7}{8}+\frac{11}{12}-\frac{5}{6}=\frac{21}{24}+\frac{22}{24}-\frac{20}{24}=\frac{23}{24}\).

Ответ: 1) \(\frac{7}{8}\); 2) \(\frac{5}{24}\); 3) \(-\frac{1}{72}\); 4) \(\frac{37}{70}\); 5) \(\frac{4}{45}\); 6) \(\frac{17}{20}\); 7) \(\frac{89}{912}\); 8) \(\frac{2}{5}\); 9) \(\frac{23}{24}\).