Answer:
126 cm^2
Step-by-step explanation:
Let's name the point where the two triangles meet on the horizontal line point Z. Then the area of the left triangle is ...
A(left) = (1/2)(XZ)(AX)
and the are of the right triangle is ...
A(right) = (1/2)(ZY)(YC)
Now, we know that AX = YC = (1/2)AD, so the sum of the two triangle areas is ...
A(triangle total) = A(left) +A(right)
= (1/2)(AX)(XZ +ZY)
Since XZ +ZY = AB, we have the total triangle area equal to ...
A(triangle total) = (1/2)((1/2)AD)(AB) = (1/4)(AD)(AB)
Now (AD)(AB) = 168 cm^2, so the unshaded area is ...
A(unshaded) = A(rectangle) -A(triangle total)
= 168 cm^2 -(1/4)(168 cm^2)
= 126 cm^2
The unshaded area in the figure is 126 cm^2.
