Bess throws the Frisbee out 4 times * 20 meters each time = <<4*20=80>>80 meters.
She then throws it back which doubles the distance traveled to 80 meters * 2 = <<80*2=160>>160 meters.
Holly throws the Frisbee out 5 times * 8 meters = <<5*8=40>>40 meters.
So in total, Holly and Bess have thrown the Frisbees 160 + 40 = <<160+40=200>>200 meters.
#### 200