6.

1. 408-270+21008:808 = 138 + 26 = 164

2. 71370:234+695-50 = 305 + 695 - 50 = 950

3. 280084:28-125-8 = 10003 - 125 - 8 = 9870

4. (327+541350:450):3 = (327+1203):3 = 1530:3 = 510

5. (31460+1040):(150-2400:120) = 32500:(150-20) = 32500:130 = 250

6. (78213-75209)-207-45*308 = 3004 - 207 - 13860 = -11063

7. (992341:269+780)-325:5 = (3689+780)-65 = 4469-65 = 4404

8. 434280:517-306+27449 = 840 - 306 + 27449 = 27983