b. 47.25 ft^2
You can find the area of the figure separately like( Area of the rectangle + Area of the triangle ) .
So the base of the triangle can be found :12ft -9ft = 3ft
Area of the triangle = 1/2 × 3 × 4.5 = 6.75 ft^2
Area of the rectangle = 9 × 4.5 = 40.5 ft^2
Then add the area to get the area of the whole figure : 6.75 +40.5 = 47.25 ft^2