`a) -5/9 + 5/9 : ( 1 2/3 - 2 1/12)`
`= -5/9 + 5/9 : (-5/12)`
`= -5/9 + (-4/3)`
`= -17/9`
``
`b) 3/4 . 15/7 + 3/7 . 13/4`
`= 3/7 . 15/4 + 3/7 . 13/4`
`= 3/7 . ( 15/4 + 13/4)`
`= 3/7 . 7`
`= 3`
``
`c) 1.4 . 15/49 - ( 4/5 + 2/3) : 2 1/5`
`= 7/5 . 15/49 - 22/15 : 11/5`
` = 3/7 - 2/3`
`= -5/21`
``
`d) -7/25 . 11/3 + (-7)/25 . 2/13 - 18/25`
`= -7/25 . ( 11/3 + 2/13) - 18/25`
`= -7/25 . 1 - 18/25`
`= -7/25 - 18/25`
`= -1`