`a)`

`11/19 + 19/18 + 8/19 - 1/18 + 5,2`

`= (11/19 + 8/19) + (19/18 - 1/18) + 5,2`

`= 19/19 + 18/18 + 5,2`

`= 1+1 + 5,2`

`= 7,2`

`b)`

`11/24 - 5/41 + 13/24 + 0,5 - 36/41`

`= (11/24+13/24) - (5/41 + 36/41) + 0,5`

`= 24/24 - 41/41 + 0,5`

`= 1 - 1 + 0,5`

`= 0,5`