The formula for the area of a regular polygon is mc003-1.jpg. what is the equation solved for a?

Area of a regular polygon is computed using this formula:

Area = (a * p) / 2
a = length of the apothem 
p = perimeter of the polygon

Using the above formula, we can derive the formula for a.

A = (a*p)/2
A*2 = a*p
(2A)/p = a     or     a = (2*A) / p