9976+865)+135=976+(865+135)=976+1000=1976
891+(799+109)=(891+109)+799=1000+799=1799
(2/5+1/9)+3/5=(2/5+3/5)+1/9=1+1/9=9/9+1/9=10/9
19/11+(8/13+3/11)=(19/11+3/11)+8/13=22/11+8/13=22/11+8/13=2+8/13=26/13+8/13=34/13
16.88+9.76+3.12=(16.88+3.12)+9.76=20+9.76=29.76
72.68+17.16+82.64=72.68+(17.16+82.64)=72.68+100=172.68
(976+865)+135=976+(865+135)
=976+1000=1976