2 вариант: 1) 7/8 − 1/2; 2) 5 − 2 2/3; 3) 3 3/5 + 3 11/15; 4) 9 11/42 − 5 11/14; 5) 4/7 × 3/2; 6) 2 4/5 × 15; 7) 25/27 : 5/9; 8) 4 1/5 : 1 1/4.

1. \(\frac{7}{8}-\frac{1}{2}=\frac{7}{8}-\frac{4}{8}=\frac{3}{8}\).
2. \(5-2\frac{2}{3}=5-\frac{8}{3}=\frac{15-8}{3}=\frac{7}{3}=2\frac{1}{3}\).
3. \(3\frac{3}{5}+3\frac{11}{15}=6+\frac{9}{15}+\frac{11}{15}=6\frac{20}{15}=7\frac{1}{3}\).
4. \(9\frac{11}{42}-5\frac{11}{14}=9\frac{11}{42}-5\frac{33}{42}=4-\frac{22}{42}=3\frac{20}{42}=3\frac{10}{21}\).
5. \(\frac{4}{7}\times\frac{3}{2}=\frac{12}{14}=\frac{6}{7}\).
6. \(2\frac{4}{5}\times15=\frac{14}{5}\times15=42\).
7. \(\frac{25}{27}:\frac{5}{9}=\frac{25}{27}\times\frac{9}{5}=\frac{5}{3}=1\frac{2}{3}\).
8. \(4\frac{1}{5}:1\frac{1}{4}=\frac{21}{5}:\frac{5}{4}=\frac{21}{5}\times\frac{4}{5}=\frac{84}{25}=3\frac{9}{25}\).

Ответ: 1) 3/8; 2) 2 1/3; 3) 7 1/3; 4) 3 10/21; 5) 6/7; 6) 42; 7) 1 2/3; 8) 3 9/25.