Ответ:

Пошаговое объяснение:

2)

-1,6x *(-5y) = 8xy

-7a - 9b + a + 11b = -6a + 2b

a - (a - 8) + (12 + a) = a - a + 8 + 12 + a = a + 20

-3(c - 5) + 6(c + 3) = -3c + 15 + 6c + 18 = 3c + 33

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4)

= -5,4x + 2 - 6 + 3,4x + 3,2x - 16 = 1,2x - 20

при x = -5/6

1,2x - 20 = 1,2*(-5/6) - 20 = -1 - 20 = -21