39. Приведите дроби к общему знаменателю: 1) 5/6 и 3/4; 2) 7/8 и 5/6; 3) 3/8 и 11/16; 4) 5/28 и 9/14; 5) 3/7 и 4/9; 6) 11/15 и 3/8; 7) 13/16 и 11/12; 8) 3/8, 5/6 и 1/4; 9) 3/14, 4/21 и 5/6.

Приводим каждую группу дробей к наименьшему общему знаменателю.

1. НОЗ(6, 4) = 12: 5/6 = 10/12, 3/4 = 9/12.
2. НОЗ(8, 6) = 24: 7/8 = 21/24, 5/6 = 20/24.
3. НОЗ(8, 16) = 16: 3/8 = 6/16, 11/16 = 11/16.
4. НОЗ(28, 14) = 28: 5/28 = 5/28, 9/14 = 18/28.
5. НОЗ(7, 9) = 63: 3/7 = 27/63, 4/9 = 28/63.
6. НОЗ(15, 8) = 120: 11/15 = 88/120, 3/8 = 45/120.
7. НОЗ(16, 12) = 48: 13/16 = 39/48, 11/12 = 44/48.
8. НОЗ(8, 6, 4) = 24: 3/8 = 9/24, 5/6 = 20/24, 1/4 = 6/24.
9. НОЗ(14, 21, 6) = 42: 3/14 = 9/42, 4/21 = 8/42, 5/6 = 35/42.