2/7= 2.85....
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Нет через час і 20 мин
14+16=30
40/30=1,3333
19 т.к. последний разрез делит на 2 части
2 1/2 : (1/2х + 5/12) - 1 5/6 = 2/3
2 1/2 : (1/2х +5/12) = 2/3 + 1 5/6 = 4/6 + 1 5/6 = 1 9/6 = 2 3/6 = 2 1/2
1/2х + 5/12 = 2 1/2 : 2 1/2 = 1
1/2х = 1 - 5/12 = 12/12 - 5/12 = 7/12
х = 7/12 : 1/2 = 7/12 * 2 = 7/6 = 1 1/6
х = 1 целая 1/6
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Проверка:
2 1/2 : (1/2 * 1 1/6 + 5/12) - 1 5/6 = 2/3
2 1/2 : (7/12 + 5/12) - 1 5/6 = 2/3
2 1/2 : 1 - 1 5/6 = 2/3
2 3/6 - 1 5/6 = 1 9/6 - 1 5/6 = 4/6 = 2/3
-2х, при х = 15
-2×15=-30
при х =-5,5
-2×(-5,5)=11
при х = 0,8
-2×0,8=-1,6