(8/9 + 10/7 +6/11)+(3/11 - 3/7 +4/9)
=(8/9 +4/9) +(10/7 -3/7)+( 6/11 +3/11)
=4/3 +1 + 9/11
=44/33 +1+27/33
=71/33 +1
=3又5/33