278. Вычислите значение выражения: 1) 8 1/14 - 3 3/7; 2) 7 5/12 - 3 7/24; 3) 12 11/12 - 5 13/18.

Решение:

1. \( 8 \frac{1}{14} - 3 \frac{3}{7} = \frac{113}{14} - \frac{24}{7} = \frac{113}{14} - \frac{48}{14} = \frac{65}{14} = 4 \frac{9}{14} \)
2. \( 7 \frac{5}{12} - 3 \frac{7}{24} = \frac{89}{12} - \frac{79}{24} = \frac{178}{24} - \frac{79}{24} = \frac{99}{24} = \frac{33}{8} = 4 \frac{1}{8} \)
3. \( 12 \frac{11}{12} - 5 \frac{13}{18} = \frac{155}{12} - \frac{103}{18} = \frac{465}{36} - \frac{206}{36} = \frac{259}{36} = 7 \frac{7}{36} \)

Ответ: 1) \( 4 \frac{9}{14} \); 2) \( 4 \frac{1}{8} \); 3) \( 7 \frac{7}{36} \).