30. Вычислите: 1) 4/9 − 3/7; 2) 5/8 + 7/12; 3) 15/18 − 7/12; 4) 11/12 + 5/18; 5) 13/16 − 7/32; 6) 2/3 − 5/39.

1. \(\frac{4}{9}-\frac{3}{7}=\frac{28}{63}-\frac{27}{63}=\frac{1}{63}\).
2. \(\frac{5}{8}+\frac{7}{12}=\frac{15}{24}+\frac{14}{24}=\frac{29}{24}=1\frac{5}{24}\).
3. \(\frac{15}{18}-\frac{7}{12}=\frac{5}{6}-\frac{7}{12}=\frac{10}{12}-\frac{7}{12}=\frac{1}{4}\).
4. \(\frac{11}{12}+\frac{5}{18}=\frac{33}{36}+\frac{10}{36}=\frac{43}{36}=1\frac{7}{36}\).
5. \(\frac{13}{16}-\frac{7}{32}=\frac{26}{32}-\frac{7}{32}=\frac{19}{32}\).
6. \(\frac{2}{3}-\frac{5}{39}=\frac{26}{39}-\frac{5}{39}=\frac{21}{39}=\frac{7}{13}\).

Ответ: 1) \(\frac{1}{63}\); 2) \(1\frac{5}{24}\); 3) \(\frac{1}{4}\); 4) \(1\frac{7}{36}\); 5) \(\frac{19}{32}\); 6) \(\frac{7}{13}\).