To find the area of the rectangle within the composite shape, we first need to find the total area of the composite shape and then subtract the areas of the two congruent right triangles.
The two congruent right triangles each have an area of 1/2 * base * height = 1/2 * 3 * 4 = 6 square inches. Since there are two of them, their combined area is 2 * 6 = 12 square inches.
Since the total area of the composite shape is 40 square inches, the area of the rectangle can be found by subtracting the area of the two triangles from the total area:
40 - 12 = 28 square inches
Therefore, the area of the rectangle within the composite shape is 28 square inches.