`a)2/3+1/3:x=-1/5`
` => 1/3 :x = -1/5 - 2/3`
`=> 1/3 :x = -13/15`
`=> x = 1/3 : (-13)/15`
`=> x = -5/13`
Vậy `x=-5/13`
`b) (2/7.x+3/7).2-3/7=-2`
`=> (2/7x + 3/7).2 = -2 + 3/7`
`=> (2/7x+3/7).2 = -11/7`
`=> 2/7x+3/7 = -11/7 : 2`
`=> 2/7x + 3/7 = -11/14`
`=> 2/7x = -11/14 - 3/7`
`=> 2/7x = -17/14`
`=> x = -17/14 : 2/7`
`=> x = -17/4`
Vậy `x=-17/4`