Đáp án+Giải thích các bước giải:
$a.15-(30+x)=x-(27-|-8|)$
$15-30-x=x-(27-8)$
$-15-x=x-19$
$⇔-15+19=x+x$
$⇔4=2x$
$⇔x=4:2$
$⇒x=2$
$b.(12x-4^3).8^3=4.8^4$
$(12x-2^6).2^9=2^2.2^{12}$
$12x-2^6=2^2.2^{12}:.2^9$
$12x-64=32$
$12x=96$
$⇒x=8$
$c.[(10-x).2+51]:3-2=3$
$[(10-x).2+51]:3=5$
$(10-x).2+51=15$
$(10-x).2=-36$
$10-x=-18$
$x=28$
$d.8≤|x-6|<9$
$=>|x-6|=8$
$⇔$\(\left[ \begin{array}{l}x-6=8\\x-6=-8\end{array} \right.\)$<=>$\(\left[ \begin{array}{l}x=14\\x=-2\end{array} \right.\)