`a) ( -20/3 )^3 . ( -18/5 )^3`

`= ( -20/3 . ( -18)/5)^3`

`= ( 4 . 9 )^3`

`= 36^3`

`= 46656`

`b) ( -5/4 )^2 : ( -35/24 )^2`

`= ( -5/4 : ( -35)/24 )^2`

`= ( 5/4 . 24/35 )^2`

`= ( 6/7 )^2`

`= 36/49`

`c) A = ( -1/3)^3 . ( -1/3 )^2 . ( -1/3 )`

`A = ( -1/3 )^( 3 + 2 + 1 )`

`A = ( -1/3 )^6`

`A = ( 1/3 )^6`

`A = 1/729`