`1/2 + 9/10 + 5/6 - 11/14 - 1/3 + (-4)/35`
`= ( 1/2 + 9/10 + 5/6 - 11/14 - 1/3) - 4/35`
`=( 105/210 + 189/210 + 175/210 - 165/210 - 70/210) - 4/35`
`= 39/35 - 4/35`
`= 1`
``
`b) ( 18/23 + 7/12 )+ ((-13)/19 - 3/4) + ((-6)/19 + 5/23)`
`= 18/23 + 7/12 - 13/19 - 3/4 - 6/19 + 5/23`
`= ( 18/23 + 5/23) + ( 7/12 - 3/4) - ( 13/19 + 6/19)`
`= 1 + (-1/6) - 1`
`= (1 - 1) - 1/6`
`= 0 - 1/6`
`= -1/6`
``
`c) 4/3 + (-5)/6 + (-1)/4`
`= 16/12 - 10/12 - 3/12`
`=1/4`
``
`d) 5/6 - 7/5 + 17/30`
`=25/30 - 42/30 + 17/30`
`=0`