@Thỏ
`-x` + `11/30` = `19/30` + `x` : `2`
`-x` + `11/30` = `19/30` + `x` : `2`
`-x` - `x` : `2` = `19/30` - `11/30`
`-x` + `-x` . `1/2` = `4/15`
`-x` . (`1` + `1/2`) = `4/15`
`-x` . `3/2` = `4/15`
`-x` = `4/15` : `3/2`
`-x` = `8/45`
⇒ `x = -8/45`
Vậy `x = -8/45`
