Question: ![enter image description here](https://i.stack.imgur.com/MW1Mt.jpg)

This problem has bothered me for quite some time and I can't solve it. I have even tried to make a construction, but it sometimes tips to the left and sometimes tips to the right :).

When we submerge the body in the water the water pushes it up. That is an action. At the same time the body pushes water down. That is a reaction. So the balance should be maintained.

But, since the water level rises the hydrostatic pressure on the bottom is greater so the right side should go down.

There is another similar problem but it's not the same. 

Please help.

Answer: 
If you consider everything put in the right side of balance scale as one system, only the internal forces are changed which will not affect the balance. 
No external force is applied and hence the balance will be maintained.
Let $V$ be the volume of the hanging block, $A$ the area of the water surface, $\rho$ the density of water, and $g$ the acceleration due to gravity.

The extra hydrostatic force felt by the bottom of the container after lowering the block is
$$\Delta F = \rho gA\Delta h,$$
where $\Delta h$ is the change in water height ($\rho g \Delta h$ would be the change in hydrostatic pressure). Because water is not compressible, $A\Delta h$ must be the volume of the submerged block.
$$\Delta F = \rho g V.$$
Notice that this is exactly equal to the buoyant force on the block, so the two new forces created after the block is submerged negate each other.