644.
1)
(1/3 - 5/8) * (- 6/7)
1/3 - 5/8 = 8/24 - 15/24 = - 7/24
- 7/24 * (-6/7) = 1/3
2)
(- 5/12 - 7/30) : 13/15
- 5/12 - 7/30 = - 25/60 - 14/60 = - 39/60
-39/60 : 13/15 = - 39/60 * 15/13 = - 3/4
3)
(-3/4 - 1/6) : (-1 3/8)
-3/4 - 1/6 = - 9/12 - 2/12 = - 11/12
- 11/12 : (-1 3/8) = -11/12 : (-11/8) = -11/12 * (-8/11) = 2/3
4)
(1/4 - 5/18) * 36
1/4 - 5/18 = 9/36 - 10/36 = - 1/36
- 1/36 * 36 = -1
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645.
1)
(-5/12 - 3/4) : 2 1/3 + 5 1/3 * 0,75
1. -5/12 - 3/4 = -5/12 - 9/12 = - 14/12
2. - 14/12 : 2 1/3 = -14/12 : 7/3 = -14/12 * 3/7 = - 2/4 = - 1/2
3. 5 1/3 * 0,75 = 16/3 * 75/100 = 16/3 * 3/4 = 4
4) - 1/2 + 4 = 3 1/2