`a) 24/126 - (-5)/28`
`=4/21 + 5/28`
`= 16/84 + 15/84`
`= 31/84`
``
`b) -3 1/2 - 1 1/3`
`= -7/2 - 4/3`
`=-21/6 - 8/6`
`= -29/6`
``
`c) 2/3 - (-1)/4 + 1/21 + 1/12`
`= 2/3 + 1/4 + 1/21 + 1/12`
`= 56/84 + 21/84 + 4/84 + 7/84`
`= 22/21`
``
`d) (-1)/3 - (-3)/5 - 1/6 + 1/43 - (-3)/7 + (-1)/2 - 1/35`
`= -1/3 + 3/5 - 1/6 + 1/43 + 3/7 - 1/2 - 1/35`
`= (-1/3 + 3/5 + 3/7 - 1/35) - ( 1/6 + 1/2) + 1/43`
`=(-35/105 + 63/105 + 45/103 - 3/105) - ( 2/12 + 6/12) + 1/43`
`= 2/3 - 2/3 + 1/43`
`= 0 + 1/43`
`= 1/43`
