`a) 2/3 - 4( 1/2 + 3/4)`
`= 2/3 - 4 . 5/4`
` = 2/3 - 5`
`= -13/3`
``
`b) (-1/3 + 5/6) . 11 - 7`
`= 1/2 . 11 - 7`
`= 11/2 - 7`
`=-3/2`
``
`c) (-23)/16 . 19/25 + 6/25 . (-23)/16`
`= (-23)/16 . ( 19/25 + 6/25)`
`= (-23)/16 . 1`
`= (-23)/16`
``
`d) (-13)/17 . 55/27 - 28/27 . (-13)/17`
`= (-13)/17 . ( 55/27 - 28/27)`
`= (-13)/17 . 1`
`= (-13)/27`