Giúp vs ạ , cmon!!!!!

`#`dminh

`a, (-10)/11 . 8/9 + 7/8 . 10/11`

`= 10/11 . (-8)/9 + 7/8 . 10/11`

`= 10/11 . ((-8)/9 + 7/8)`

`= 10/11 . (-1)/72`

`= (-5)/396`

``

`b, ((-40)/51 . 0,32 . 17/20) : 64/75`

`= ((-40)/51 . 17/20 . 32/10) : 64/75`

`= ((-2)/3 . 32/100) : 64/75`

`= (-16)/75 : 64/75`

`= (-16)/75 . 75/64`

`= ((-16) . 75)/(75 . 64)`

`= (-16)/64`

`= (-1)/4`