How to solve this number 4

Answer:
The correct answer is B.
Explanation:
The corresponding sides of similar triangles are proportional. In this case, PQ and ST are a pair of corresponding sides and RQ and TU are other pairs of corresponding sides.
Hence,
[tex]\dfrac{\text{PQ}}{\text{ST}}=\dfrac{\text{RQ}}{\text{TU}}\\\\\text{or, }\dfrac{n}{13}=\dfrac{15}{5}[/tex]