The sizes of seven exterior angles of an octagon are: 42, 110, 13, 67, 55, 11 and 53. What is the size of the eighth exterior angle?

9°

Step-by-step explanation:

Always some of exterior angle of any polygon is 360

42 + 110 + 13 + 67 + 55 + 11 + 53 + x = 360

351 + x = 360

x = 360 - 351

x = 9

9 degrees.

Step-by-step explanation:

For ALL polygons, the exterior angles add up to 360 degrees.

Therefore the 8th exterior angle = 360 - (42+110+13+67+55+11+53)

= 360 - 351

= 9 degrees.