`a,`

`15/12 + 5/13 - ( 3/12 + 18/13 )`

`= 15/12 + 5/13 - 3/12 - 18/13`

`= ( 15/12 - 3/12 ) + ( 5/13 - 18/13 )`

`= 1 + ( - 1 )`

`= 1 - 1`

`= 0`

`b,`

`5/16 - ( 4/15 - 3/16 ) + 17/30`

`= 5/16 - 4/15 + 3/16 + 17/30`

`= ( 5/16 + 3/16 ) + ( - 4/15 + 17/30 )`

`= 1/2 + 3/10`

`= 4/5`

`c,`

`1/6 - [ 1/6 - ( 1/4 + 9/12 )]`

`= 1/6 - [ 1/6 - 1/4 - 9/12 ]`

`= 1/6 - 1/6 + 1/4 + 9/12`

`= ( 1/6 - 1/6 ) + ( 1/4 + 9/12 )`

`= 0 + 1`

`= 1`

`d,`

`5/19 + 8/11 + 14/19 + 3/2 - 30/11`

`= ( 5/19 + 14/19 ) + ( 8/11 - 30/11 ) + 3/2`

`= 1 + ( - 2 ) + 3/2`

`= 1 - 2 + 3/2`

`= - 1 + 3/2`

`= 1/2`

`#`Nguyencanhthinh`#`
`*** Hoidap247`