3)
6786×32-32+320×3+[50+300×(200×3+5)]=
=6786×32-32+320×3+[50+300×(600+5)]=
=6786×32-32+320×3+(50+300×605)=
=6786×32-32+320×3+(50+181500)=
=6786×32-32+320×3+181550=
=217152-32+960+181550=
=217120+960+181550=
=218080+181550=
=399630
