Answer:
3.78 m on the left side of the seesaw
Step-by-step explanation:
The net torque in this situation is zero, so the torque from each side of the pivot point must balance each other out:
(50.0 kg x 10.0 m/s^2)(3.4m) = (450 N) r
Solve for r, and you get 3.78 on the left side.
Hope this helps!