Question

In the diagram below, BC is an altitude of ABD. To the nearest whole unit, what is the length of CD?

Answer 1

For the answer to the question above, I'll show my solution on how you can solve your problem.
AC² + BC² = AB² 
5² + 12² = AB² 
25 + 144 = AB² 
169 = AB² 
13 = AB 

Triangle ABC is proportional to triangle ADB. 

AC = AB 
AB    AD 

5 = 13 
13  AD 

5AD = 169 

AD = 169/5 

AD = 33.8 

AD = AC + CD 

33.8 = 5 + CD 
So the answer is

CD = 28.8 

Answer 2

Answer:

Actually the answer is 56, so D.

Step-by-step explanation: