Answer:
272 ft²
Explanation:
You want the area of a figure composed of a rectangle and a triangle.
Composition
The dashed line in the diagram helps you see that the shape is that of a triangle combined with a rectangle. The base length of the triangle is shown as 8 ft, but the height is not shown. It needs to be computed.
The rectangle is 12 ft from its bottom to the dashed line, so the triangle height is ...
20 ft - 12 ft = 8 ft . . . . . . . height of triangle
Triangle
The area of a triangle is given by the formula ...
A = 1/2bh . . . . . base b, height h
The area of this triangle is ...
A = 1/2(8 ft)(8 ft) = 32 ft²
Rectangle
The formula for the area of a rectangle is ...
A = LW
For this rectangle, the area is ...
A = (20 ft)(12 ft) = 240 ft²
Total area
The area of the figure is the sum of the areas of its parts.
garden area = (32 ft²) +(240 ft²)
garden area = 272 ft²