3. Выполните действия: а) 3/8 + 5/6; б) 7/16 - 13/24; в) 5/12 + 7/5.

Решение:

1. а) 3/8 + 5/6
   НОК(8, 6) = 24.
   \\(\frac{3}{8} + \frac{5}{6} = \frac{3 \times 3}{8 \times 3} + \frac{5 \times 4}{6 \times 4} = \frac{9}{24} + \frac{20}{24} = \frac{9 + 20}{24} = \frac{29}{24} \>
2. б\) 7/16 - 13/24
   НОК(16, 24) = 48.
   \\(\frac{7}{16} - \frac{13}{24} = \frac{7 \times 3}{16 \times 3} - \frac{13 \times 2}{24 \times 2} = \frac{21}{48} - \frac{26}{48} = \frac{21 - 26}{48} = \frac{-5}{48} \>
3. в\) 5/12 + 7/5
   НОК(12, 5) = 60.
   \\(\frac{5}{12} + \frac{7}{5} = \frac{5 \times 5}{12 \times 5} + \frac{7 \times 12}{5 \times 12} = \frac{25}{60} + \frac{84}{60} = \frac{25 + 84}{60} = \frac{109}{60} \>

Ответ: а\) 29/24; б) -5/48; в) 109/60.