`a)`

`0,6 + 2/3`

`= 6/10 + 2/3`

`= 3/5 + 2/3`

`= 9/15 + 10/15`

`= 19/15`

`b)`

`1/3 - (-0,4)`

`= 1/3 + 0,4`

`= 1/3 + 4/10`

`= 1/3 + 2/5`

`= 5/15 + 6/15`

`= 11/15`

`c)`

`3,5 - ((-2)/7)`

`= 35/10 + 2/7`

`= 7/2 + 2/7`

`= 49/14 + 4/14`

`= 53/14`

`d)`

`2,5 - (-3/4)`

`= 25/10 + 3/4`

`= 5/2 + 3/4`

`= 10/4 + 3/4`

`= 13/4`

`e)`

`(-5)/12 + 0,75`

`= (-5)/12 + 75/100`

`= (-5)/12 + 3/4`

`= (-5)/12 + 9/12`

`= 4/12`

`= 1/3`