Using proportions, it is found that the length of AC is of 15 units.
<h3>What is a proportion?</h3>A proportion is a fraction of a total amount, and the measures are related using a rule of three.
The ratios in this problem are given as follows:
.
.
.
The entire length is of 18 units, AB is half of that, hence:
AB = 0.5 x 18 = 9 units.
BC is two thirds of the length from 6 to 15, hence:
BC = 2/3 x (15 - 6) = 6
Thus, the length of AC is:
AC = 9 + 6 = 15 units.
More can be learned about proportions at brainly.com/question/24372153
#SPJ1