19,17+(-12,73)= -23,45+18,62= -5/6+3/12= 7/9+(-9/10)= 8 3/5+(-6 11/15)=

19,17+(-12,73)=6,44
-23,45+18,62=-4,83
-5/6+3/12=-10/12+3/12=-7/12
7/9+(-9/10)=70/90+(-81/90)=-21/90=-7/30
8 3/5+(-6 11/15)=43/5+(-101/15)=129/15-101/15=28/15=1 13/15