Tìm x

a,2/3+1/3÷3x=1/5

b,1/4x+1/2=2/5

c,1/2-2/5x=(-1)/3

d,1/3x-2/5=2/3(x-1)

Giải thích các bước giải:

a.Ta có:

$\dfrac23+\dfrac13:3x=\dfrac15$ 

$\to\dfrac13:3x=-\dfrac7{15}$

$\to 3x=\dfrac13:\dfrac{-7}{15}$

$\to 3x=-\dfrac57$

$\to x=-\dfrac5{21}$

b.Ta có:

$\dfrac14x+\dfrac12=\dfrac25$

$\to \dfrac14x=-\dfrac1{10}$

$\to x=\dfrac{-2}5$

c.Ta có:

$\dfrac12-\dfrac25x=\dfrac{-1}3$

$\to -\dfrac25x=-\dfrac56$

$\to x=\dfrac{25}{12}$

d.Ta có:

$\dfrac13x-\dfrac25=\dfrac23(x-1)$

$\to \dfrac13x-\dfrac25=\dfrac23x-\dfrac23$

$\to \dfrac23x-\dfrac13x=\dfrac23-\dfrac25$

$\to\dfrac13x=\dfrac4{15}$

$\to x=\dfrac45$