Since AB and BC are both parts of the same line segment, AB+BC=AC. If you do substitution and some algebra, you get 6+11=17. So the answer is 17 cm. Hope that helped!
AC will equal to 17 since it's a full line segment that contains A & C as endpoints. While b is the midpoint which does not have to be equally dissected. With adding AB & BC together will have the full value of the line segment.
