4. Вычислите: 1) 5/7 + 1/4; 2) 7/15 − 3/10; 3) 11/18 − 4/9; 4) 7/30 + 9/20; 5) 11/16 − 5/12; 6) 5/18 + 4/27.

1. \(\frac{5}{7}+\frac{1}{4}=\frac{20}{28}+\frac{7}{28}=\frac{27}{28}\).
2. \(\frac{7}{15}-\frac{3}{10}=\frac{14}{30}-\frac{9}{30}=\frac{5}{30}=\frac{1}{6}\).
3. \(\frac{11}{18}-\frac{4}{9}=\frac{11}{18}-\frac{8}{18}=\frac{3}{18}=\frac{1}{6}\).
4. \(\frac{7}{30}+\frac{9}{20}=\frac{14}{60}+\frac{27}{60}=\frac{41}{60}\).
5. \(\frac{11}{16}-\frac{5}{12}=\frac{33}{48}-\frac{20}{48}=\frac{13}{48}\).
6. \(\frac{5}{18}+\frac{4}{27}=\frac{15}{54}+\frac{8}{54}=\frac{23}{54}\).

Ответ: 1) \(\frac{27}{28}\); 2) \(\frac{1}{6}\); 3) \(\frac{1}{6}\); 4) \(\frac{41}{60}\); 5) \(\frac{13}{48}\); 6) \(\frac{23}{54}\).