A square has an unknown side length of x feet. It is transformed into a rectangle by increasing its length by 12 feet and decreasing its width by 4 feet. (a) Determine a trinomial expression for the area of the new rectangle in terms of x. Create an area model to illustrate how you found your answer.

(b) If the area of the new rectangle is equal to the area of the original square, then find the numerical side length of the original square, x. Show how you found your answer.