The area of the shaded region is 78 square inches. All angles are right angles and all measurements are given in inches. What is the perimeter of the non-shaded region?

The total area = 9 x 10 = 90 sq in

The shaded area = 78 sq in

Subtracting, the central area = 12 sq in

Since the height is 2 in, the width must = 6 in