Hello, ncooks!
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Find the area of the shaded region. Code:
9
* - - - - - - - *
|:::::::::::::::*
|:::::::::::* | 2
|:::::::* ..*
|:::* *:::*
* *:::::::|
| *:::::::::::*
13 *::::::::::* | 2
|:::::::* ..|
|:::* *:::*
* *:::::::|
| *:::::::::::|
*:::::::::::::::|
|:::::::::::::::|
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The area of the rectangle is: . 
Assuming that the diagonal lines are parallel,
. . the white regions are two congeuent parallelograms,
. . each with base 2 and height 9.
The white region has area: .  \:=\:36\text{ cm}^2)
Therefore, the area of the shaded region is: . 
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An easier way . . .
Remove the white strips and push the shaded regions together. Code:
9
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|:::::::::::::::*
|:::::::::::*:::|
|:::::::*:::::::|
9 |:::*:::::::::::*
*:::::::::::*:::|
|:::::::*:::::::|
|:::*:::::::::::|
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