2,5x+4/7=-1,5 Giúp tôi giải nha

Đáp án:

 $a) 2,5x+\dfrac{4}{7}= -1,5$

$⇒ \dfrac{5}{2}x= -\dfrac{3}{2}-\dfrac{4}{7}$

$⇒ \dfrac{5}{2}x= \dfrac{-21}{14}-\dfrac{8}{14}$

$⇒ \dfrac{5}{2}x= -\dfrac{29}{14}$

$⇒ x= (-\dfrac{29}{14}):\dfrac{5}{2}$

$⇒ x= \dfrac{-29}{14}.\dfrac{2}{5}$

$⇒x= -\dfrac{29}{35}$

$\text{Vậy x= $-\dfrac{29}{35}$}$

$b)$ $\text{60%.x}$ $+\dfrac{2}{3}.x=1368$

$⇒ x.(\dfrac{3}{5}+\dfrac{2}{3})= 1368$

$⇒ x.(\dfrac{9}{15}+\dfrac{10}{15})= 1368$

$⇒x. \dfrac{19}{15}= 1368$

$⇒ x= 1368:\dfrac{19}{15}$

$⇒ x= \dfrac{1368}{1}.\dfrac{15}{19}$

$⇒ x= \dfrac{72.19.15}{19}$

$⇒ x= 1080$

$\text{Vậy x=1080}$