Help me please ! I know this question is easy for some but please help me

  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.

30

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