Вычислите: 1/3 + 2/5; 1/2 − 1/4; 8/7 − 1; 1/4 − 1/5; 1/2 + 3/7; 1/3 + 1/4; 2/3 − 2/5; 1/5 − 1/6; 1/2 + 1/4; 7/6 − 1; 7/25 − 4/15; 3/10 + 1/6; 2/5 − 11/30; 3/8 + 7/20; 1/6 − 1/7.

Чтобы сложить или вычесть дроби с разными знаменателями, привожу их к общему знаменателю.

1. \(\frac{1}{3}+\frac{2}{5}=\frac{5}{15}+\frac{6}{15}=\frac{11}{15}\).
2. \(\frac{1}{2}-\frac{1}{4}=\frac{2}{4}-\frac{1}{4}=\frac{1}{4}\).
3. \(\frac{8}{7}-1=\frac{8}{7}-\frac{7}{7}=\frac{1}{7}\).
4. \(\frac{1}{4}-\frac{1}{5}=\frac{5}{20}-\frac{4}{20}=\frac{1}{20}\).
5. \(\frac{1}{2}+\frac{3}{7}=\frac{7}{14}+\frac{6}{14}=\frac{13}{14}\).
6. \(\frac{1}{3}+\frac{1}{4}=\frac{4}{12}+\frac{3}{12}=\frac{7}{12}\).
7. \(\frac{2}{3}-\frac{2}{5}=\frac{10}{15}-\frac{6}{15}=\frac{4}{15}\).
8. \(\frac{1}{5}-\frac{1}{6}=\frac{6}{30}-\frac{5}{30}=\frac{1}{30}\).
9. \(\frac{1}{2}+\frac{1}{4}=\frac{2}{4}+\frac{1}{4}=\frac{3}{4}\).
10. \(\frac{7}{6}-1=\frac{7}{6}-\frac{6}{6}=\frac{1}{6}\).
11. \(\frac{7}{25}-\frac{4}{15}=\frac{21}{75}-\frac{20}{75}=\frac{1}{75}\).
12. \(\frac{3}{10}+\frac{1}{6}=\frac{9}{30}+\frac{5}{30}=\frac{14}{30}=\frac{7}{15}\).
13. \(\frac{2}{5}-\frac{11}{30}=\frac{12}{30}-\frac{11}{30}=\frac{1}{30}\).
14. \(\frac{3}{8}+\frac{7}{20}=\frac{15}{40}+\frac{14}{40}=\frac{29}{40}\).
15. \(\frac{1}{6}-\frac{1}{7}=\frac{7}{42}-\frac{6}{42}=\frac{1}{42}\).