Đáp án:
Bài 1: $x=-\dfrac{626}{415}$
Bài 2: $\left\{ \begin{array}{l}x=-\dfrac{15}{8}\\y=-5\end{array} \right.$
Giải thích các bước giải:
Bài 1:
$(2,5-3x):\dfrac{7}{3}=\Bigg(\dfrac{8}{5}+2x\Bigg):\Bigg(-\dfrac{8}{17}\Bigg)$
$↔ \dfrac{3(2,5-3x)}{7}=\dfrac{10x+8}{5}.\dfrac{17}{-8}$
$↔ \dfrac{7,5-9x}{7}=\dfrac{170x+136}{-40}$
$↔ -40(7,5-9x)=7(170x+136)$
$↔ 360x-300=1190x+952$
$↔ 830x=-1252$
$↔ x=-\dfrac{626}{415}$
Bài 2:
$x:y=3:8$
$↔ \dfrac{x}{3}=\dfrac{y}{8}$
$=\dfrac{x-y}{3-8}$
$=\dfrac{25}{8.(-5)}$
$=\dfrac{-5}{8}$
$→ \left\{ \begin{array}{l}x=3.\dfrac{-5}{8}=-\dfrac{15}{8}\\y=8.\dfrac{-5}{8}=-5\end{array} \right.$
