If Julien swam for the whole week, then the total distance in meters that he covered is 50*7 = <<50*7=350>>350 meters
Sarah swam twice the distance covered by Julien, which is 2*50 = <<2*50=100>>100 meters
Sarah's total for the whole week is 100*7 = <<100*7=700>>700 meters
If Jamir swam 20 meters more than Sarah, he covered 100+20 = <<20+100=120>>120 meters
Jamir's total for the whole week is 120*7 = <<120*7=840>>840 meters
The combined distance for all of them is 840+700+350 = <<840+700+350=1890>>1890 meters
#### 1890