You need to download the app Photo math
Answer:

And we know that the level is decreasing 20% each day so then we can use the following model for the problem

Where t represent the number of days and L the level for this case we want to fnd the level after two days so then t =2 and replacing we got:

Step-by-step explanation:
For this case we know that the initial volume of water is:

And we know that the level is decreasing 20% each day so then we can use the following model for the problem

Where t represent the number of days and L the level for this case we want to fnd the level after two days so then t =2 and replacing we got:

X^3-1 rewrite as x^3-1^3
differences of cubes formula: a^3-b^3=(a-b)(a^2+ab+b^2)
a=x, b=1
(x-1)(x^2+x*1+1^2)
(x-1)(x^2+x+1)