Total area = rectangle area + triangle area = 12×9 + 1/2×6×6 = 108 + 18 = 126 cm². For a shaded or remaining part, find each simple area first, then subtract the part that is removed. Use the perpendicular height, not a slanted side, because the height must make a right angle with the base. The answer is in square units because area measures the surface covered by the triangle.