2,5+(-4 1/3)+(-1 13/15)

2,5-4 1/3- 1 13/15= 2 15/30- 4 10/30- 1 26/30= -(4 10/30+ 1 26/30)+2 15/30= -6 6/30 + 2 15/30= -3 21/30= -3,7