How far from the shaft at P a 200N vertical force must act so as to create the same moment as produced by the 75N, at P?

1.125 m

As we know that the moment is the cross product of the distance and the force we will try to apply the same here. So let the distance be y, then the force of 200N will act downward. 

Since Torque by the two forces are equal hence 

$75\times 3 cos 60^o = 200 \times y \times cos 60^o $

$\Rightarrow y = \frac{225}{200} = 1.125 m$