1.a) 7/8 + 7/8; 2.a) 7/12 + 7/3; 3.a) 12/8 + 3/3; 4.a) 9/4 + 7/3; 5.a) 1/36 + 7/9; 6.a) 2/5 + 1/6; 7.a) 2/20 + 1/6; 8.a) 2 5/8 + 3 4/9 + 1 7/18

Решение:

1. \( \frac{7}{8} + \frac{7}{8} = \frac{14}{8} = \frac{7}{4} = 1\frac{3}{4} \)
2. \( \frac{7}{12} + \frac{7}{3} = \frac{7}{12} + \frac{28}{12} = \frac{35}{12} = 2\frac{11}{12} \)
3. \( \frac{12}{8} + \frac{3}{3} = \frac{3}{2} + 1 = 1\frac{1}{2} + 1 = 2\frac{1}{2} \)
4. \( \frac{9}{4} + \frac{7}{3} = \frac{27}{12} + \frac{28}{12} = \frac{55}{12} = 4\frac{7}{12} \)
5. \( \frac{1}{36} + \frac{7}{9} = \frac{1}{36} + \frac{28}{36} = \frac{29}{36} \)
6. \( \frac{2}{5} + \frac{1}{6} = \frac{12}{30} + \frac{5}{30} = \frac{17}{30} \)
7. \( \frac{2}{20} + \frac{1}{6} = \frac{1}{10} + \frac{1}{6} = \frac{3}{30} + \frac{5}{30} = \frac{8}{30} = \frac{4}{15} \)
8. \( 2\frac{5}{8} + 3\frac{4}{9} + 1\frac{7}{18} = (2+3+1) + (\frac{5}{8} + \frac{4}{9} + \frac{7}{18}) = 6 + (\frac{45}{72} + \frac{32}{72} + \frac{28}{72}) = 6 + \frac{105}{72} = 6 + \frac{35}{24} = 6 + 1\frac{11}{24} = 7\frac{11}{24} \)

Ответ: 1. 1 3/4; 2. 2 11/12; 3. 2 1/2; 4. 4 7/12; 5. 29/36; 6. 17/30; 7. 4/15; 8. 7 11/24.