I am stuck on the answer for this question

Answer:
12/13
Step-by-step explanation:
[tex]\sf Cos \ x = \dfrac{adjacent \ side \ to \ \angle x}{hypotenuse}\\\\[/tex]
[tex]\sf = \dfrac{XY}{ZX}\\\\=\dfrac{36}{39}\\\\=\dfrac{36 \div3}{39 \div 3}\\\\=\dfrac{12}{13}[/tex]