` \color{#0074D9}{#n}\color{#0088DD}{q}\color{#3399FF}{o}\color{#66AAFF}{c}\color{#99CCFF}{c} `

`a) 2/5 + 3/4 : x = -1/2 `

`3/4 : x = -1/2 - 2/5 `

`3/4 : x = -9/10 `

`x = 3/4 : (-9/10) `

`x = 3/4 . (-10/9) `

`x = -5/6 `

Vậy `x=-5/6`

`b) 5/7 - 2/3 . x = 4/5 `

`2/3x =5/7 - 4/5 `

`2/3x = -3/35 `

`x = -3/35 : 2/3 `

`x = -3/35 . 3/2 `

`x = -9/70 `

Vậy `x=-9/70`

`c) 1/2 . x + 3/5 . x = -2/3 `

`11/10x = -2/3 `

`x = -2/3 : 11/10 `

`x = -2/3 . 10/11 `

`x = -20/33 `

Vậy `x=-20/33 `

`d) 4/7 . x - x = -9/14 `

`-3/7x = -9/14 `

`x = -9/14 : (-3/7) `

`x = -9/14 . (-7/3) `

`x = 3/2 `

Vậy `x=3/2`