7целых 2\3a-1,5b-5\6 при a=5\46; b=-4\9; c=14\15

А = 5/46;   b = - 4/9;   c = 14/15
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7 целых 2/3 * 5/46 - 1,5 * (-4/9) - 5/6 * 14/15 = 13/18

1) 7 целых 2/3 * 5/46 = 23/3 * 5/46 = (1*5)/(3*2) = 5/6
2) 1,5 * (-4/9) = 15/10 * (-4/9) = - (5*2)/(5*3) = - 2/3
3) 5/6 * 14/15 = (1*7)/(3*3) = 7/9
4) 5/6 - (-2/3) = 5/6 + 4/6 = 9/6 = 3/2 
5) 3/2 - 7/9 = 27/18 - 14/18 = 13/18
ответ: 13/18.