giúp em với mn ơi em cảm ơn

`a, (-3)/4 . 12/(-5) . (-25/6)`

`= -( 3/4 . 12/5 . 25/6 )`

`= -( 3/2^2 . (2^2 . 3)/5 . (5^2)/(2.3) )`

`= -15/2`

`b, (-2). (-38)/21 . (-7)/4 . (-3/8)`

`= 2 . 7/4 . 38/21 . 3/8`

`= 7/2 . 38/21 . 3/8`

`= 19/3 . 3/8`

`= 19/8`

`c, (11/12 : 33/16) . 3/5`

`= 11/12 . 16/33 . 3/5`

`= 11/12 . 3/5 . 16/33`

`= 33/60 . 16/33`

`= 16/60`

`= 4/15`

`d, 7/23 . [(-8/6) - 45/18]`

`= 7/23 . ( -24/18 - 45/18)`

`= 7/23 . (-69)/18`

`= -7/6`

`|__L__|`