`a) 3/7 + 4/7 . x = 3/14`
`4/7 . x = 3/14 - 3/7`
`4/7 . x = -3/14`
`x = -3/14 : 4/7`
`x= -3/8`
Vậy `x = -3/8`
``
`b) (-2)/3 . x + 1/2x - 3/7 = -5/6`
`((-2)/3 + 1/2) x = -5/6 + 3/7`
`-1/6 . x = -17/42`
`x = -17/42 : (-1/6)`
`x= 17/7`
Vậy `x = 17/7`
``
`c) 2/3 x - 1/2 x = 5/12`
`( 2/3 - 1/2) x = 5/12`
`1/6 x= 5/12`
`x = 5/12 : 1/6`
`x= 5/2`
Vậy `x = 5/2`
``
`(5x - 1) ( 2x - 1/3) = 0`
⇒ \(\left[ \begin{array}{l}5x-1=0\\2x- \frac{1}{3}=0\end{array} \right.\)
\(\left[ \begin{array}{l}5x=0+ 1\\2x=0 + \frac{1}{3}\end{array} \right.\)
\(\left[ \begin{array}{l}5x=1\\2x=\frac{1}{3}\end{array} \right.\)
\(\left[ \begin{array}{l}x=1 : 5\\x=\frac{1}{3} : 2\end{array} \right.\)
\(\left[ \begin{array}{l}x=\frac{1}{5}\\x=\frac{1}{6}\end{array} \right.\)
Vậy `x ∈ { 1/5 ; 1/6}`
