Labeled CXR showing position of different valves.

https://radiologykey.com/valvular-heart-disease/

Look at where the cusps are pointing → upwards therefore aortic. if cusps were downward → then mitral valve would be the right answer

another link I found helpful

I was stuck between mitral and aortic and went with aortic because the L ventricle looks enlarged, possibly hinting that the patient had aortic stenosis.