Вычисли: 1) 12/12 + 6/24; 2) 1/81 + 3/27; 3) 9/30 + 7/20; 4) 7/70 + 21/90; 5) 19/6 + 12/7; 6) 5/25 + 9/45; 7) 20/12 + 8/54.

1. \(\frac{12}{12}+\frac{6}{24}=1+\frac14=\frac54\).
2. \(\frac{1}{81}+\frac{3}{27}=\frac{1}{81}+\frac19=\frac{1}{81}+\frac{9}{81}=\frac{10}{81}\).
3. \(\frac{9}{30}+\frac{7}{20}=\frac{3}{10}+\frac{7}{20}=\frac{6}{20}+\frac{7}{20}=\frac{13}{20}\).
4. \(\frac{7}{70}+\frac{21}{90}=\frac{1}{10}+\frac{7}{30}=\frac{3}{30}+\frac{7}{30}=\frac13\).
5. \(\frac{19}{6}+\frac{12}{7}=\frac{133}{42}+\frac{72}{42}=\frac{205}{42}=4\frac{37}{42}\).
6. \(\frac{5}{25}+\frac{9}{45}=\frac15+\frac15=\frac25\).
7. \(\frac{20}{12}+\frac{8}{54}=\frac53+\frac{4}{27}=\frac{45}{27}+\frac{4}{27}=\frac{49}{27}=1\frac{22}{27}\).

Ответ: 1) \(\frac54\); 2) \(\frac{10}{81}\); 3) \(\frac{13}{20}\); 4) \(\frac13\); 5) \(4\frac{37}{42}\); 6) \(\frac25\); 7) \(1\frac{22}{27}\).