Question

In the diagram, AB = 12, DX = 2.5, and BX = 5. Find CD. Show all work.

Answer 1

I found your complete question in another source.
 See attached image. 
 For this case what you should see is that you have two similar triangles.
 We then have the following relationship:
 ((AB) / (BX)) = ((CD) / (DX))
 We cleared CD:
 CD = ((AB) / (BX)) * (DX)
 Substituting the values:
 CD = ((12) / (5)) * (2.5)
 CD = 6
 Answer: 
 CD = 6