Giải giúp mình với ạ

Đáp án:

`a)`

`- 4/7 . 3/8 + (-4)/7 . 5/8 + 1 4/7`

`= - 4/7 . ( 3/8 + 5/8 ) + 1 4/7`

`= - 4/7 . 1 + 1 4/7`

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

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

`= 0+1 = 1`

`b)`

`6/7 + 5/8 : 5 − 3/16 . (-2)^2`

`= 6/7 + 5/8 . 1/5 - 3/16 . 4`

`= 6/7 + 5/40 - 12/16`

`= 6/7 + 1/8 − 3/4`

`= 6/7 + (1/8 - 6/8)`

`= 6/7 + (-5/8)`

`= 48/56 − 35/56`

`= 13/56`

`c)`

`28/15 . 0 , 75 − ( 23/20 + 25 % ) : 7/3`

`= 7/5 − ( 23/20 + 1/4) . 3/7`

`= 7/5 − 7/5 . 3/7`

`= 7/5. (1 - 3/7)`

`= 7/5. (7/7 - 3/7)`

`= 7/5 .4/7`

`= 4/5`