SOSSSSSSSSSSSSSSSSSSSSSSSS giúp e với ạaaaaa, e cảm ơn, ai giúp e e vote cho 5sao aaaaaaaa<3

`1,`

`a, 25/42-20/63 `

`= 75/126 - 40/126`

`= 35/126`

`=5/18`

`b, 9/50-13/75-1/6`

`=27/150-26/150-25/150`

`=(27-26-25)/150`

`=-24/150`

`=-4/25`

`c, 2/15-2/65-4/39`

`= (2/15 - 4/39) - 2/65`

`= 2/65 - 2/65` `

`= (2 - 2)/65`

`= 0/65`

`= 0`

`d, 9/10-15/16. 5/12-11/15-7/20`

`=9/10-25/64-11/15-7/20`

`= 163/320-11/15 -  7/20`

`=-43/192-7/20`

`=-551/960`