17 + (-5)= 17-5=12
-21+ 19=19-21=-2
-8+(-43)=-(8+43)=-51
-15+(-18)=-(15+18)=-33
-0,5+6=5,5
-2,4+(-3,2)=-5,6
6,1+-(8,3)= -(8,3-6,1)=-2,2
-3,84+4,16=0,32
-2/9+5/9=3/9
-4/7+2/7=-2/7
5/8+(-7/12)=15/24-14/24=1/24
-1+3/5=-5/5+3/5=-2/5
-2+1,3/4=-8/4+ 7/4=-1/4
3+(-1 2/7)=21/7-9/7=12/7=1 5/7
2 2/3 + (-1 5/6)= 8/3-11/6=16/6-11/6=5/6
-5 1/3+4,5=-16/3+9/2=-32/6+27/6=-5/6