Answer:
Step-by-step explanation:
Let represent the edge of the tank with x and the radius of the first sphere with x/2;
The amount of the water = Volume of the tank - Volume of the sphere
= 
on the second cube ; the radius of the sphere =
;
Also the number of sphere here is = 8
The amount of water = 
For the third figure ; the radius of the sphere is = 
Also the number of sphere here is = 64
The amount of water = 
= 
In the fourth tank ; 512 sphere illustrates that in a single row; that more than one 8 sphere is present i.e 8³ = 512
then the radius will be = 
The amount of water = 
= 
This implies that alll the three cube shaped tanks are identical and hold equal amount of water.