Answer:
43.5 square units
Explanation:
You want to know the area of shading in a 12 by 7 rectangle with a white right triangle of side length 9 removed.
Triangle area
The area of the white triangle is ...
A = 1/2bh
A = 1/2(9)(9) = 40.5 . . . . square units
Rectangle area
The area of the rectangle is ...
A = LW
A = (12)(7) = 84 . . . . square units
Shaded area
The shaded area is the area of the rectangle that is not included in the triangle.
Shaded area = 84 -40.5 = 43.5 . . . . square units
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Additional comment
The given figure cannot actually be constructed. The triangle is too large to be inscribed in the rectangle. An inscribed right triangle can have a side length between 7 and √74 ≈ 8.6.