`a)`

        `4/5 + 3/5.(-2/15)`

`=4/5 +(-6/75)`

`=20/25- 2/25`

`= 18/25`

`b)`

        `-5/17. 31/33 - 5/17. 2/33+ 22/17`

`= (-5/17). 31/33 + (-5/17). 2/33 + 22/17`

`= (-5/17). (31/33+2/33)+22/17`

`=(-5/17). 1+22/17`

`=(-5/17)+22/17`

`= 17/17=1`

`c)`

        `28/15 . 3/4 - (11/20+1/4):5/7`

`= 28/4 . 3/15 - (11/20+5/20). 7/5`

`= 7. 1/5 - 16/20 . 7/5`

`= 7/5 - 4/5 . 7/5`

`= 35/25- 28/25`

`= 7/25`

`#` `Uh`