you have to add the forces applied by the mass...
if u take a mass of 200 g and place it 4 m from the pivot, then you have to put the 100g 8m from the pivot on the opposite side to balance it...therefore the 200g is apllying 2 N of force and 100g --> 1 N of force
therefore the total force is 3 N..
add this to the weight of the disc that is 200g = 2 N
therefore tha answer is 2+3= 5N
it depends on the masses u have taken
a certain combination could give 7N too as the answer..
hope it helped u
