`@``text{Bơ}`

`a) 7/6 - 1/6 : 2/3`

`= 7/6 - 1/6 . 3/2`

`= 7/6 - 1/4`

`= 14/12 - 3/12`

`= 11/12`

`b) 13,3 . 45 - 44 . 13,3`

`= 13,3 . (45 - 44)`

`= 13,3 . 1`

`= 13,3`

`c) 2021 - (1/3)^2 . 3^2`

`= 2021 - (1/3 . 3)^2` 

`= 2021 - 1^2`

`= 2021 - 1`

`= 2020`

`d) ((-3)/4 + 2/5) : 3/7 + (3/5 + (-1)/4) : 3/7`

`= (-3/4 + 2/5) . 7/3 + (3/5 - 1/4) . 7/3` 

`= 7/4 . [(-3/4 + 2/5) + (3/5 - 1/4)]`

`= 7/3 . [-3/4 + 2/5 + 3/5 - 1/4]`

`= 7/3 . [(-3/4 - 1/4) + (2/5 + 3/5)]`

`= 7/3 . [(-1) + 1]`

`= 7/3 . 0`

`= 0`