A = x(x − 4) − 0.5(8)(x − 4) − 4(8) is the correct equation.
This equation calculates the painted area by finding the total area of the floor (x(x-4)), subtracting the area of the stage (0.5(8)(x-4)), and subtracting the area of the closet (4(8)). The remaining area is the painted area.