Solve the problem. Chivi's Mexican restaurant pledges 12% of any food purchased on the third Wednesday of each month to the Cystic Fibrosis Foundation. How much food must be purchased for the donation to be at least $1,152?

$9,600
$13,824
$9,216
$10,416.67

The formula for finding the sum of the interior angles of a polygon is the same, whether the polygon is regular or irregular. So you would use the formula (n-2) x 180, where n is the number of sides in thepolygon. If you draw a diagonal in the square, that forms two triangles.