1) (176+343)-243=176+(343-243)=176+100=276
2) (684+915)-484=(684-484)+915=200+915=1115
3) (259+101)-59=(259-59)+101=200+101=301
4) 1287-(487+164)=(1287-487)-164=800-164=636
5) 971-(235+371)=(971-371)-235=600-235=365
6) 5393-(1393+158)=(5393-1393)-158=4000-158=3842