The amount of torque that a mass is based the distance from the fulcrum. The red blocks will create counter-clockwise motion, and the green will create clockwise motion. We need the red and green to be equal.
6 + 4 + 2(2) = 2(3) + 5 + x
14 = 11 + x
x = 3
So the green block should be placed at 3 on top the other two blocks.
