Answer:
Julie weighs 35 lbs, Ted weighs 70 lbs, Mike weighs 105 lbs.
Explanation:
Let the weight of Julie be

Given:
Ted weighs twice as much as Julie
Weight of Ted =

Mike weighs three times as much as Julie.
Weight of Mike =

Together, Ted, Mike, and Julie weigh 210 lbs.

Solving above we get;

Hence Julie weight is 35 lbs.
Weight of Ted =

Hence Ted weight is 70 lbs.
Weight of Mike =

Hence Mike weight is 105 lbs.