Answer:
We need to find the force exerted by the water on the beaker,
This force will be subtracted from the reading of the top scale and be added to the force on the bottom scale - this is the buoyant force.
That is, the bottom scale will support an additional weight equal to the weight of the water displaced by the block and this force will then be subtracted from the top spring scale,
ρ = 1000 kg/m^3 is the mass density of the water
Mb = ρb Vb for the mass of the block
Vb = 3 kg / 4500 kg/m^3 = 6.67E-4 m^3 for the volume of the block
Mw = 1000 kg/m^3 * 6.67E-4 m^3 = .667 kg for the mass of the water displaced
Ww = .667 kg * 9.80 m/s^2 = 6.64 N weight of water displaced
Wo = 3 kg * 9.80 m/s^2 = 29.4 N original reading of spring scale
29.4 - 6.64 = 22.8 N weight of spring scale after immersion
Wbo = (1 + 2.6) kg * 9.80 m/s^2 = 35.3 N original weight on bottom scale
Wbf = (35.3 + 6.64) N = 41.9 N weight on bottom scale after providing support for metal block