0,9 * 11/12 - (4 11/15 - 1 7/12) : 8,4 = 9/20 = 0,45
1) 4 11/15 - 1 7/12 = 4 44/60 - 1 35/60 = 3 9/60 = 3 3/20
2) 0,9 * 11/12 = 9/10 * 11/12 = 33/40
3) 3 3/20 : 8,4 = 63/20 : 84/10 = 63/20 * 10/84 = 9/24 = 3/8
4) 33/40 - 3/8 = 33/40 - 15/40 = 18/40 = 9/20
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в десятичных дробях:
1) 3 3/20 = 3,15
2) 33/40 = 0,825
3) 3,15 : 8,4 = 0,375
4) 0,825 - 0,375 = 0,45