4) 1/3 - (-2/5) =
5)- 2,7 + (-1/3) =
6) 7,1/11 - (-2,2/3) =

1/3 - (-2/5) = 5/15 + 6/15 = 11/15- 2,7 + (- 1/3) = - 2 7/10 - 1/3 = - 2 21/30 - 10/30 = - 2 31/30 = - 3 1/307 1/11 - (- 2 2/3) = 7 3/33 + 2 22/33 = 9 25/33