Answer: The square of the orbital period, T, of a planet is equal to the cube of the average distance, A, of the planet from the Sun.
Explanation:
In mathematics, A number or variable 'a' to its second power is said to be square of 'a' i.e.
is the square of a.
A number or variable 'b' to its third power is said to be cube of 'b' i.e.
is the cube of b.
In the given equation:

Here,
is square of T.
And
is cube of A.
Therefore, The square of the orbital period, T, of a planet is equal to the cube of the average distance, A, of the planet from the Sun.