TÍNH NHANH Ạ thank you mng

`{-3}/4 + 3/7 + {-2}/8 + 4/9 + 4/7`

`= -3/4 + 3/7 - 1/4 + 4/9 + 4/7`

`= ( -3/4 - 1/4 ) + ( 3/7 + 4/7 ) + 4/9`

`= -1 + 1 + 4/9`

`= 0 + 4/9`

`= 4/9`

`c)`

`3/4 + {-5}/6 - 11/{-12}`

`= 3/4 - 5/6 + 11/12`

`= 18/24  - 20/24 + 22/24`

`= { 18 - 20 + 22 }/24`

`= 10/12`