Đáp án:
+$\dfrac{25}{51}$
++$\dfrac{38}{7}$
+++$\dfrac{-28}{15}$ ,$\dfrac{4}{3}$
Giải thích các bước giải:
+ $\left ( 0,25-30,6x \right ).\dfrac{1}{3}-\dfrac{1}{4}= \dfrac{-31}{6}$
$\Rightarrow 0,25-30,6x= 3.\left ( \dfrac{-31}{6}+\dfrac{1}{4} \right )$
$\Rightarrow 0,25-30,6x= \dfrac{-59}{4}$
$\Rightarrow 15= 30,6x$
$\Rightarrow x= \dfrac{25}{51}$
++ $\left ( 0,5x-\dfrac{3}{7} \right ):\dfrac{1}{2}= \dfrac{8}{7}$
$\Rightarrow 0,5x-\dfrac{3}{7}= \dfrac{16}{7}$
$\Rightarrow 0,5x= \dfrac{19}{7}$
$\Rightarrow x= \dfrac{38}{7}$
+++ $ \left | x+\dfrac{4}{15} \right |-\left (-3,75 \right )= -2,15 $
$\Rightarrow \left | x+\dfrac{4}{15} \right |= \dfrac{8}{5}$
$\Rightarrow x+\dfrac{4}{15}= \dfrac{8}{5}\Rightarrow x= \dfrac{4}{3}$
$x+\dfrac{4}{15}= \dfrac{-8}{5}\Rightarrow x= \dfrac{-28}{15}$
