`a,`

`(5/7 + 5/9 - 5/11) / (15/7 + 15/9 - 15/11)`

`= [5 . (1/7 + 1/9 - 1/11)] / [15 . (1/7 + 1/9 - 1/11)]`

`= 5 / 15`

`= 1/3`

`b,`

`(4 + 4/73 - 4/115) / (5 + 5/73 - 1/23)`

`= (4 + 4/73 - 4/115) / (5 + 5/73 - 5/115)`

`= [4 . (1 + 1/73 - 1/115)] / [5 . (1 + 1/73 - 1/115)]`

`= 4/5`

`c,`

`32/(3.7) + 6/(7.41) + 9/(41.10) + 1/(10.51) + 19/(51.14)`

`= (35 - 3)/(3.7) + (41 - 35)/(7.41) + (50 - 41)/(41.10) + (51 - 50)/(10.51) + (70 - 51)/(51.14)`

`= 35/(3.7) - 3/(3.7) + 41/(7.41) - 35/(7.41) + 50/(41.10) - 41/(41.10) + 51/(10.51) - 50/(10.51) + 70/(51.14) - 51/(51.14)`

`= 5/3 - 1/7 + 1/7 - 5/41 + 5/41 - 1/10 + 1/10 - 5/51 + 5/51 - 1/14`

`= 5/3 - 1/14`

`= 70/42 - 3/42`

`= 67/42`

`d,`

`2/(3.5) + 4/(5.9) + 2/(3.15) + 8/(15.23)`

`= 2/(3.5) + 4/(5.9) + 6/(9.15) + 8/(15.23)`

`= (1/3 - 1/5) + (1/5 - 1/9) + (1/9 - 1/15) + (1/15 - 1/23)`

`= 1/3 - 1/23`

`= 20/69`