Lm Giúp Em Với :<<<

`a) 1 4/13 + 15/22 + 9/13 + 7/22 - 2`

`= 17/13 + 15/22 + 9/13 + 7/22 - 2`

`= ( 17/13 + 9/13 ) + ( 15/22 + 7/22 ) - 2`

`= 2 + 1 - 2`

`= 1`

`b) -3/7 . 15/23 + ( -3/23 ) . 8/7 + 9/21`

`= -3/7 . 15/23 - 3/7 . 8/23 + 3/7`

`= -3/7 . ( 15/23 + 8/23 ) + 3/7`

`= -3/7 . 1 + 3/7`

`= 0`

`c) 4 7/12 - ( 11 1/24 + 5 7/12 )`

`= 4 7/12 - 11 1/24 - 5 7/12`

`= ( 4 7/12 - 5 7/12 ) - 11 1/24`

`= [ ( 4 - 5 )( 7/12 - 7/12 ) ] - 11 1/24`

`= -1 - 11 1/24`

`= [ ( -1 - 11 )( 0 + 1/24 ) ]`

`= -12 1/24`

`d) 3/7 : 21/4 - 3/7 : 13/4`

`= 3/7 . 4/21 - 3/7 . 4/13`

`= 3/7 . ( 4/21 - 4/13 )`

`= 3/7 . (( 52 - 84 )/273)`

`= 3/7 . ( -32/273 )`

`= -32/637`