Introduction:
In order to calculate the relative density of the solid and the liquid, we need to understand the concept of density and how it is affected by the buoyant force. Density is a measure of how much mass is contained within a given volume. The relative density, also known as specific gravity, compares the density of a substance to the density of a reference substance.

Given Information:
- Weight of the solid in air: 200g
- Weight of the solid in water: 160g
- Weight of the solid in the liquid: 170g

Calculating Density of the Solid:
The density of a substance can be calculated using the formula: Density = Mass / Volume.

Calculating Volume of the Solid:
To calculate the volume of the solid, we will use the Archimedes' principle, which states that the weight of the liquid displaced by a submerged object is equal to the buoyant force acting on the object.

Calculating the Volume of the Solid in Water:
The weight of the solid in water is 160g. This weight difference is due to the buoyant force acting on the solid when it is submerged in water. The weight of the water displaced by the solid is equal to this weight difference.

Calculating the Volume of the Solid in the Liquid:
Similarly, the weight of the solid in the liquid is 170g. This weight difference is also due to the buoyant force acting on the solid when it is submerged in the liquid. The weight of the liquid displaced by the solid is equal to this weight difference.

Calculating the Density of the Solid:
Now that we have the volume of the solid in both water and the liquid, we can calculate the density of the solid using the formula: Density = Mass / Volume.

Calculating the Relative Density of the Liquid:
The relative density of the liquid can be calculated by comparing its density to the density of water, which is commonly used as a reference substance.

Conclusion:
The relative density of the solid can be calculated by dividing its density by the density of water, while the relative density of the liquid can be calculated by dividing its density by the density of water. These calculations will give us a quantitative measure of how dense the solid and the liquid are in comparison to water.