a) 1/2x-1/2=-2/5 b) x-1/5=1/6+ -7/30 c) 1/2x+1/5x= -17/30 giúp mình vs nhé

$a)$ $\dfrac{1}{2}x-\dfrac{1}{2}=-\dfrac{2}{5}$

$⇒\dfrac{1}{2}x-\dfrac{1}{2}+\dfrac{1}{2}=-\dfrac{2}{5}+\dfrac{1}{2}$

$⇒\dfrac{1}{2}x=\dfrac{1}{10}$

$⇒2\cdot \dfrac{1}{2}x=\dfrac{1\cdot \:2}{10}$

$⇒x=\dfrac{1}{5}$

`Vậy` $x=\dfrac{1}{5}$

________________________________

$b)$ $x-\dfrac{1}{5}=\dfrac{1}{6}+\dfrac{\left(-7\right)}{30}$

$⇒x-\dfrac{1}{5}=\dfrac{1}{6}-\dfrac{7}{30}$

$⇒x-\dfrac{1}{5}=\dfrac{5}{30}-\dfrac{7}{30}$

$⇒x-\dfrac{1}{5}=\dfrac{5-7}{30}$

$⇒x-\dfrac{1}{5}=\dfrac{-2}{30}$

$⇒x-\dfrac{1}{5}=-\dfrac{1}{15}$

$⇒x-\dfrac{1}{5}+\dfrac{1}{5}=-\dfrac{1}{15}+\dfrac{1}{5}$

$⇒x=\dfrac{2}{15}$

`Vậy` $x=\dfrac{2}{15}$

________________________________

$c)$ $\dfrac{1}{2}x+\dfrac{1}{5}x=-\dfrac{17}{30}$

$⇒\dfrac{1}{2}x\cdot \:30+\dfrac{1}{5}x\cdot \:30=-\dfrac{17}{30}\cdot \:30$

$⇒21x=-17$

$⇒x=-\dfrac{17}{21}$

`Vậy` $x=-\dfrac{17}{21}$