Đáp án:
$- ( x - 3 + 85 ) = ( x + 70 - 71 ) - 5$
$- (x + 82) = (x - 1) - 5$
$-x - 82 = x - 1 - 5$
$-x - 82 = x - 6$
$⇒ -x - 82 + 82 = x - 6 + 82$
$-x = x + 76$
$-x - x = x + 76 - x$
$-2x = 76$
$⇒\dfrac{-2x}{-2} = \dfrac{76}{-2}$
$x = \dfrac{76}{-2}$
$\text{Vậy x = -38}$
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