Answer: C could be located at two possible points: C=-3 or C=-33
Explanation:
If CD = 15, this simply means that it is 15 units long. In order to find the other point, we can add or subtract CD from D.
Add:
D + CD = -3
(-18 + 15) = -3
Subtract:
D - CD = -33
(-18 - 15) = -33
I hope this helps :)