Answer:
45
Step-by-step explanation:
what is the area of a triangle (At) ?
At = base line × height / 2 = 12×12/2 = 72 in²
what is the area of a rectangle (Ar) ?
Ar = length × width (or height - however you see or name the second dimension)
so, the area of that inner rectangle is 3×9 = 27 in²
now the main question is about the area of the triangle without the inner rectangle.
this is simply At - Ar = 72 - 27 = 45 in²
that's it. you only need to translate the English sentence into the corresponding mathematical expressions and use the mathematical operators just as the sentence states.
we did exactly and nothing else than what the original problem statement said.
