Question 1113528
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The area of the original rectangular board is the product of its dimensions  20*12 = 240 square inches.


The area of triangle is half the product of the base length by its height  {{{(1/2)*15*9}}} = 67.5 square inches.


The area of the piece of wood which is left is the difference  240 - 67.5 = 172.5 square inches.
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