Based on the diagram shown above, the area of the shaded region in terms of π is 432 - 54π square inches.
In Mathematics and Geometry, the area of a rectangle can be calculated by using the following mathematical equation:
Area of rectangle = length × width
By substituting the given side lengths into the formula for the area of a rectangle, we have the following;
Area of rectangle = 18 × (6 + 12 + 6)
Area of rectangle = 432 square inches.
In Mathematics and Geometry, the area of a circle with radius (r) can be calculated by using this formula:
Area of circle = π

Area of circle = π ×

Area of circle = 9π square inches.
Area of circle = π ×

Area of circle = 36π square inches.
Area of circle = π ×

Area of circle = 9π square inches.
Now, we can determine the area of the shaded region as follows;
Area of the shaded region = 432 - 9π - 9π - 36π
Area of the shaded region = 432 - 54π square inches.