To find the area of the rectangle within the composite shape, we first need to calculate the area of the two congruent right triangles.
The area of one right triangle can be calculated using the formula: \[ \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} \] Given that the base (width) of each triangle is 3 inches and the height is 4 inches, we can calculate the area of one triangle:
\[ \text{Area of one triangle} = \frac{1}{2} \times 3 \times 4 = \frac{1}{2} \times 12 = 6 \text{ square inches} \]
Since there are two congruent triangles, the total area of the triangles is:
\[ \text{Total area of triangles} = 2 \times 6 = 12 \text{ square inches} \]
Now, we know the total area of the composite shape, which is 40 square inches. To find the area of the rectangle, we can subtract the total area of the triangles from the total area of the composite shape:
\[ \text{Area of rectangle} = \text{Total area of composite shape} - \text{Total area of triangles} \] \[ \text{Area of rectangle} = 40 - 12 = 28 \text{ square inches} \]
Thus, the area of the rectangle within the composite shape is 28 square inches.
Therefore, the correct response is: 28 square inches.