- 5/13+ (-7/13)= 3/11 +(-8/11)= - 9/17 + 13/17 = - 2/5 + (-2/15)= - 2/5 +3/4= -11/27+5/18= -3/11+ (-7/11)= 6/13+(-8/13)= - 8/17 + 11/17 = - 1/4 + (- 3/16 ) = -3/4 +2/5= - 5/36+5/27 =

-5/13+(-7/13)=-5/13-7/13=-12/13 3/11+(-8/11)=3/11-8/11=-5/11 -9/17+13/17=4/17 -2/5+(-2/15)=-2/5-2/15=-6/15-2/15=-8/15 -2/5+3/4=-8/20+15/20=7/20 -11/24+5/18=-22/54+15/54=-7/54 -3/11+(-7/11)=-3/11-7/11=-10/11 6/13+(-8/13)=-2/13 -8/17+11/17=3/17 -1/4+(-3/16)=-1/4-3/16=-4/16-3/16=-7/16 -3/4+2/5=-15/20+8/20=-7/20 -5/36+5/27=-15/108+20/108=5/108