A simpler analysis of Master_Evar's challenge.
The four fixed bolts form two orthogonal axes, NS and EW, so they can be resolved separately.
Imagine the East West fixed bolts as an axle running through the disc and the 100 kg weight is placed 3m on the north side of the axle, it should be obvious that the South bolt takes no load, the triangle formed by the E-W-N bolts take the load.
Now balance the torque about the East West "axle" the weight is 3m from the axis, so the torque is 3 * 100 = 300 kgm, this must be balanced by the torque applied to the disk by the north bolt, and as it's 5 meters from the East West axle it takes 300/5 = 60 kg, So we now have N=60kg, and S=0kg
Moving to the North South "axle" the weight is 2m from the axis on the west side of the North South "axle" so the torque is 2 * 100 = 200 kgm, this must be balanced by the torque applied by the West bolt, which is 5m from the axis, so W = 200/5 = 40kg, and as before East=0kg
Adding back the weight of the disc.
So N= 60 + 25 = 85kg S = 0 + 25 = 25kg, W= 40+25 = 65kg E = 0 + 25 = 25kg,
Which is once again the same answer Master_Evar got.
This assumes as before that the bolts locations are fixed. Which makes the experimental design a bit trickier,