Answer:
a
Step-by-step explanation:
square formula for area is 
The question is worded a bit strangely (in my opinion anyway), but I think your teacher wants you to describe how exponents work.
Let's say we had the expression 
The base is 5 as its the bottom most value (think of something like the base of a tree or building). The exponent is 3.
The exponent of 3 tells the reader to multiply the base 5 by itself 3 times like so

With larger exponents, it becomes more tedious to write out all the repeated multiplications, which is why many calculators have an exponent button to save time.
This should be recognized as the difference of perfect squares which is of the form:
(a^2-b^2) and the difference of squares always factors to:
(a-b)(a+b) in this case:
(3x-8)(3x+8)
The answer would be
40,000