1) (5/6 - 2/3) * (7/8 - 1/2) * (-4) = -56

Ищем НОЗ у дробей:

5/6 - 2/3 = (НОЗ: 6) = 5*1/6 - 2*2/6 = 5/6 - 4/6 = 1/6

7/8 - 1/2 = (НОЗ: 8) = 7*1/8 - 1*4/8 = 7/8 - 4/8 = 3/8

1/6 * 3/8 = 16

16 * (-4) = -56

2) (3/8 - 1/6) * (2/9 - 2/5) * 27 = 21/29

3/8 - 1/5 = (НОЗ: 40) = 3*5/40 - 1*8/40 = 15/40 - 8/40 = 7/40

2/9 - 2/5 = (НОЗ: 45) = 2*5/45 - 2*9/45 = 10/45 - 18/45 = -8/45

7/40 * -8/45 = 7/225

7/225 * 27/1 = 21/29