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$a) -5.(-x + 7) - 3.(-x - 5) = -4.(12 - x ) + 48$
$⇔ -5x - 35 + 3x + 15 = -48 +4x + 48$
$⇔ -5x + 3x - 4x = -48 + 48 - 15 + 35$
$⇔ -2x = 20$
$⇔ x = -10$
$c) 7.(-x - 7) - 5.(-x - 3) = 12.(3 - x)$
$⇔ -7x -49 + 5x + 15 = 36 - 12x$
$⇔ -7x + 5x + 12x = 36 - 15 + 49$
$⇔ 10x = 70$
$⇔ x = 7$
$b) -2.(15 - 3x) - 4.(-7x + 8) = -5 - 9.(-2x + 1)$
$⇔ -30 + 6x + 28x - 32 = -5 + 18x - 9$
$⇔ 6x + 28x - 18x = -5 -9+30+32$
$⇔ 16x = 48$
$⇔ x = 3$
$d) 5.(-3x - 7) - 4.(-2x - 11) = 7.(4x + 10) + 9$
$⇔ -15x - 35 + 8x + 44 = 28x + 70 + 9$
$⇔ -15x + 8x - 28x = 70 + 9 - 44 + 35$
$⇔ -35x = 70$
$⇔ x = -2$