`a)`

`(``2/7 - 9/4)` `- (-3/7 +` `5/4) - (``2/4 - 9/7)`

`= 2/7 - 9/4` `+ 3/7 - 5/4` `- 2/4 + 9/7`

`= (2/7 +` `3/7 + 9/7)` `+ (- 9/4 -` `5/4 - 2/4)`

`= 14/7 - 16/4`

`= 2 - 4`

`= -2`

`b,`

`(6 -` `2/3 + 1/2)` `- (5 +` `5/3 - 3/2)` `- (3 -` `7/3 + 5/2)`

`= 6 -` `2/3 + 1/2` `- 5 - 5/3` `+ 3/2 - 3` `+ 7/3 - 5/2`

`= (6 -` `5 - 3)` `+ (- 2/3 -` `5/3 + 7/3)` `+ (1/2 +` `3/2 - 5/2)`

`= -2 -` `0/3 - 1/2`

`= -2 - 1/2`

`= -4/2 - 1/2`

`= -5/2`

`c,`

`(5/3 -` `3/7 + 9)` `- (2 +` `5/7 - 2/3)` `+ (8/7 -` `4/3 - 10)`

`= 5/3` `- 3/7 + 9` `- 2 - 5/7` `+ 2/3 + 8/7` `- 4/3 - 10`

`= (5/3 +` `2/3 - 4/3)` `+ (- 3/7 -` `5/7 + 8/7)` `+ (9 -` `2 - 10)`

`= 3/3` `+ 0/7 - 3`

`= 1 - 3`

`= -2`

`d,`

`(8 -` `9/4 + 2/7)` `- (-6 -` `3/7 + 5/4)` `- (3 +` `2/4 - 9/7)`

`= 8 -` `9/4 + 2/7` `+ 6 + 3/7` `- 5/4 - 3` `- 2/4 + 9/7`

`= (8 +` `6 - 3)` `+ (- 9/4 -` `5/4 - 2/4)` `+ (2/7 +` `3/7 + 9/7)`

`= 11` `- 16/4 + 14/7`

`= 11` `- 4 + 2`

`= 9`

`e,`

`(3 -` `1/4 + 2/3)` `- (5 -` `1/3 - 6/5)` `- (6 -` `7/4 + 3/2)`

`= 3 -` `1/4 + 2/3` `- 5 + 1/3` `+ 6/5 - 6` `+ 7/4 - 3/2`

`= (``3 - 5` `- 6) +` `(- 1/4 +` `7/4) + (``2/3 + 1/3)` `+ 6/5 - 3/2`

`= -8` `+ 6/4 + 3/3` `+ 6/5 - 3/2`

`= -8` `+ 3/2 + 1` `+ 6/5 - 3/2`

`= (``-8 + 1)` `+ (3/2 -` `3/2) + 6/5`

`= -7 + 6/5`

`= -35/5 + 6/5`

`= -29/5`