To find the distance Justin swims in 7 days, we can multiply the distance he swims each day (850m) by the number of days (7).
850m x 7 = <<850*7=5950>>5950m
To convert this distance from meters to kilometers, we divide by 1000 since there are 1000 meters in 1 kilometer.
5950m / 1000 = <<5950/1000=5.95>>5.95 kilometers
Therefore, Justin swims a total distance of 5.95 kilometers in 7 days.