a) (5x - 6) - (4x - 7) = 20x² - 35x - 24x + 42 = 20x² - 11x + 42
b) - 7y + (8 + y) + 3 = - 7y + 8 + y + 3 = - 6y + 11
c) - 9a - (4a - 7) + 8(7 + a) = - 9a - 4a + 7 + 56 + 8a = - 5a + 63
d) (5a - ab) - 4a(b + 2) = 5a - ab - 4ab - 8a = - 3a - 5ab
e) (x - 2)(2x + 4y) = 2x² + 4xy - 4x - 8y
f) (5x - 7)(4 + 2x) = 20x + 10x² - 28 - 14x = 6x + 10x² - 28
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