In the diagram below, bc is an altitude of triangle abd. to the nearest whole unit, what is the length of cd?

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