13/5-(2/3+3/5)=13/5-2/3-3/5=13/5-3/5-2/3=2-2/3=4/3
8/9-(1/2+2/9)+1/2=8/9-1/2-2/9+1/2=8/9-2/9-1/2+1/2=2/3
9/13+5/11-4/13+6/11=9/13-4/13+(5/11+6/11)=18/13
13/5-(2/3+3/5)=13/5-2/3-3/5=13/5-3/5-2/3=2-2/3=4/3
8/9-(1/2+2/9)+1/2=8/9-1/2-2/9+1/2=8/9-2/9-1/2+1/2=2/3
9/13+5/11-4/13+6/11=9/13-4/13+(5/11+6/11)=18/13