`a) 5/15 + 14/25 - 4/3 + 11/15`

`= (5/15 - 4/3 ) + ( 14/25 + 11/15)`

`= -1 + 97/75`

`= 22/75`

`b)5/20 + 1 7/11 - 25% - (18/11 - 4/9)`

`= 5/20 + 18/11 - 1/4 - 18/11 + 4/9`

`= (5/20 - 1/4 ) + ( 18/11 - 18/11 ) +4/9`

`= 0+0+4/9=4/9`

`c) -3/4 . 12/(-5) . (-25/6)`

`= -3/4 . -12/5 . (-25)/6`

`= -15/2`

`d) 2 1/9 . 2/3 + 15 8/9 . 2/3`

`= 19/9 . 2/3 + 143/9 . 2/3`

`= (19/9 + 143/9) . 2/3`

`= 162/9 . 2/3`

`= 18 . 2/3`

`= 12`