a) sai đề
b) `5/6`x - `2/3` =`1/3`
`5/6` x = `1/3` + `2/3`
`5/6` x = 1
x = 1: `5/6`
x = `6/5`
c) `5/9` - `2/9`x = `2/3`
`2/9`x =`5/9`- `2/3`
`2/9`x =`-1/9`
x = `1/9` : `2/9`
x = `-1/2
d) `4/9` + `7/3` : x = `1/5`
`7/3` : x = `1/5` - `4`/9`
`7/3`: x = `9/20`
x = `7/3` : `9/20`
x = `140/27`