Located on the top is a right triangle. ALL triangles have a total of 180 degrees within their borders. The small box in the lower-left hand corner of the triangle indicates that the given angle is a right angle, which is 90 degrees. The missing angle can be determined by adding the two known angles (90º and 35º), then subtracting the sum from 180º. On the bottom is a quadrilateral, which is a four-sided polygon. Other quadrilaterals include rectangles, trapezoids, squares, parallelograms, and others. ALL quadrilaterals have a total of 360 degrees within their borders. To find the missing angle in this quadrilateral, simply add the three known angles (141º, 79º, and 55º), then subtract the sum from 360º.













