8) The figure is a heptagon. This means the sum of the interior angles would be 180(7-2) = 5 * 180 = 900. Then this means you can say that the sum of all angles would equal 900.
(133 + 106 + 120 + 133 + (13 - 9)) + (m + m + m) = 900 -------Combine Like terms---------- 496 + 3m = 900 -------Subtraction------------ 3m = 404 --------Division-------- m = 404/3
If the answer doesn't seem right, just plug it in!
496 + 3(404/3) = 900 496 + 404 = 900 900 = 900
10) Same thing. The sum of the interior angles in a pentagon are 540.
(122 + 90 + 88 + 96) + k = 540 396 + k = 540 k = 144
11) The angle supplementary to the angle which measures 138 is 42. The sum of all the interior angles of a quadrilateral is 360. Let us call the missing INTERIOR angle x.
(104 + 98 + 42) + x = 360 244 + x = 360 x = 116 So the missing EXTERIOR angle is 180 - 116 which is 64.
12 is a bit confusing without showing you sorry :(
