When triangles are similar, ratios of corresponding side lengths are the same. The side lengths you know are CD, DU, VW, WU. (You also know CU, but you do not know the corresponding length VU.)
The ratios can be formed in any convenient way, but it is already clear that the triangles are not similar. CD = 73 is a prime number, and neither DU nor VW is a multiple of that. For example, ...
... CD/VW = 73/84 ≠ 48/55 = DU/WU
