Answer
$W =483.3 \ N$
Work Step by Step
We must consider the force caused by the board, which we know has a center of mass of 1.5 meters from the scale. Thus, we set the force on the scale equal to the forces caused by both the board and the person on the scale:
$210(3) = (3.4)(9.81)(1.5) + 1.2W \\ W =483.3 \ N$
