276. Найдите сумму: 1)5+62)60+2; 3) 1+4+2. 9 277. Вычислите значение выражения: 1)8-3; 14 278. Вычислите: 3 1) 1-2) 4-10; 3) 13-7 279. Вычислите: 3 5+6 3 16 3 1) 1-1; 2) 6-; 3) 10-5 13 55 9 20

Ответ: Решения ниже

276. 1) \(5 \frac{7}{8} + 6 \frac{3}{10} = (5 + 6) + (\frac{7}{8} + \frac{3}{10}) = 11 + (\frac{7 \cdot 5}{8 \cdot 5} + \frac{3 \cdot 4}{10 \cdot 4}) = 11 + (\frac{35}{40} + \frac{12}{40}) = 11 + \frac{47}{40} = 11 + 1 \frac{7}{40} = 12 \frac{7}{40}\) 2) \(6 \frac{3}{8} + 2 \frac{5}{9} = (6 + 2) + (\frac{3}{8} + \frac{5}{9}) = 8 + (\frac{3 \cdot 9}{8 \cdot 9} + \frac{5 \cdot 8}{9 \cdot 8}) = 8 + (\frac{27}{72} + \frac{40}{72}) = 8 + \frac{67}{72} = 8 \frac{67}{72}\) 3) \(1 \frac{8}{21} + 4 \frac{3}{14} + 2 \frac{2}{7} = (1 + 4 + 2) + (\frac{8}{21} + \frac{3}{14} + \frac{2}{7}) = 7 + (\frac{8 \cdot 2}{21 \cdot 2} + \frac{3 \cdot 3}{14 \cdot 3} + \frac{2 \cdot 6}{7 \cdot 6}) = 7 + (\frac{16}{42} + \frac{9}{42} + \frac{12}{42}) = 7 + \frac{37}{42} = 7 \frac{37}{42}\) 277. 1) \(8 \frac{9}{14} - 3 \frac{3}{7} = (8 - 3) + (\frac{9}{14} - \frac{3}{7}) = 5 + (\frac{9}{14} - \frac{3 \cdot 2}{7 \cdot 2}) = 5 + (\frac{9}{14} - \frac{6}{14}) = 5 + \frac{3}{14} = 5 \frac{3}{14}\) 2) \(7 \frac{5}{12} - 3 \frac{7}{24} = (7 - 3) + (\frac{5}{12} - \frac{7}{24}) = 4 + (\frac{5 \cdot 2}{12 \cdot 2} - \frac{7}{24}) = 4 + (\frac{10}{24} - \frac{7}{24}) = 4 + \frac{3}{24} = 4 + \frac{1}{8} = 4 \frac{1}{8}\) 3) \(12 \frac{11}{12} - 5 \frac{13}{18} = (12 - 5) + (\frac{11}{12} - \frac{13}{18}) = 7 + (\frac{11 \cdot 3}{12 \cdot 3} - \frac{13 \cdot 2}{18 \cdot 2}) = 7 + (\frac{33}{36} - \frac{26}{36}) = 7 + \frac{7}{36} = 7 \frac{7}{36}\) 278. 1) \(1 - \frac{17}{29} = \frac{29}{29} - \frac{17}{29} = \frac{12}{29}\) 2) \(4 - \frac{7}{19} = \frac{4 \cdot 19}{19} - \frac{7}{19} = \frac{76}{19} - \frac{7}{19} = \frac{69}{19} = 3 \frac{12}{19}\) 3) \(13 - 7 \frac{3}{16} = (13 - 7) - \frac{3}{16} = 6 - \frac{3}{16} = \frac{6 \cdot 16}{16} - \frac{3}{16} = \frac{96}{16} - \frac{3}{16} = \frac{93}{16} = 5 \frac{13}{16}\) 4) \(15 - 12 \frac{16}{17} = (15 - 12) - \frac{16}{17} = 3 - \frac{16}{17} = \frac{3 \cdot 17}{17} - \frac{16}{17} = \frac{51}{17} - \frac{16}{17} = \frac{35}{17} = 2 \frac{1}{17}\) 279. 1) \(1 - \frac{13}{55} = \frac{55}{55} - \frac{13}{55} = \frac{42}{55}\) 2) \(6 - \frac{9}{20} = \frac{6 \cdot 20}{20} - \frac{9}{20} = \frac{120}{20} - \frac{9}{20} = \frac{111}{20} = 5 \frac{11}{20}\) 3) \(10 - 5 \frac{12}{35} = (10 - 5) - \frac{12}{35} = 5 - \frac{12}{35} = \frac{5 \cdot 35}{35} - \frac{12}{35} = \frac{175}{35} - \frac{12}{35} = \frac{163}{35} = 4 \frac{23}{35}\) 4) \(8 - 4 \frac{5}{22} = (8 - 4) - \frac{5}{22} = 4 - \frac{5}{22} = \frac{4 \cdot 22}{22} - \frac{5}{22} = \frac{88}{22} - \frac{5}{22} = \frac{83}{22} = 3 \frac{17}{22}\)

Ответ: 276) 12 7/40, 8 67/72, 7 37/42; 277) 5 3/14, 4 1/8, 7 7/36; 278) 12/29, 3 12/19, 5 13/16, 2 1/17; 279) 42/55, 5 11/20, 4 23/35, 3 17/22.