a) 

`5/9 + 4/9 . (-1/4) `

`= 5/9 - 1/9 = 4/9`

b)

`-5/{17} . {31}/{33} + (-5/17) . 2/33 + 1 2/17`

` = -5/{17} . ( 31/33 + 2/33) + 19/17`

`= -5/{17} . 1 + 19/17`

` = -5/{17} + 19/17`

` = 14/17`

c)

`( 1 + 2/3 - 5/4) - ( 1 - 5/4) + ( 2022 - 2/3) `

`= 1 + 2/3 - 5/4 - 1 + 5/4 + 2022 - 2/3`

`= ( 1 - 1 + 2022) + ( 2/3 - 2/3) + ( -5/4 +5/4)`

` = 2022 + 0 + 0 `

` = 2022`