Выполните сложение обыкновенных дробей. Вариант 2: 1) 1/4 + 1/12; 2) 1/6 + 2/3; 3) 7/8 + 3/4; 4) 4/7 + 2/21; 5) 9/12 + 3/4; 6) 8/9 + 1/3; 7) 4/5 + 7/15.

1. \(\frac{1}{4}+\frac{1}{12}=\frac{3}{12}+\frac{1}{12}=\frac{4}{12}=\frac{1}{3}\).
2. \(\frac{1}{6}+\frac{2}{3}=\frac{1}{6}+\frac{4}{6}=\frac{5}{6}\).
3. \(\frac{7}{8}+\frac{3}{4}=\frac{7}{8}+\frac{6}{8}=\frac{13}{8}=1\frac{5}{8}\).
4. \(\frac{4}{7}+\frac{2}{21}=\frac{12}{21}+\frac{2}{21}=\frac{14}{21}=\frac{2}{3}\).
5. \(\frac{9}{12}+\frac{3}{4}=\frac{3}{4}+\frac{3}{4}=\frac{6}{4}=1\frac{1}{2}\).
6. \(\frac{8}{9}+\frac{1}{3}=\frac{8}{9}+\frac{3}{9}=\frac{11}{9}=1\frac{2}{9}\).
7. \(\frac{4}{5}+\frac{7}{15}=\frac{12}{15}+\frac{7}{15}=\frac{19}{15}=1\frac{4}{15}\).

Ответ: 1) \(\frac{1}{3}\); 2) \(\frac{5}{6}\); 3) \(1\frac{5}{8}\); 4) \(\frac{2}{3}\); 5) \(1\frac{1}{2}\); 6) \(1\frac{2}{9}\); 7) \(1\frac{4}{15}\).