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A decagon has angles that measure 170°, 140°, 130°, 145°, 140°, 145°, 150°, 150°, 130°, and x. What is x?
 

 Feb 28, 2023
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Use the formula S=(n-2)180. Since it's a decagon with 10 sides, n=10 --> S=(10-2)180=8*180=1440 so the sum of the interior angles of the decagon is 1440 degrees. The sum of all the angles listed plus x must be 1440, so we have the equation 1440=x+1200 (I just simplified all those). Solving you get \(x=\boxed{240}\)

 Feb 28, 2023

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