Is it proper to say a x ray or an x ray?

Answer 1

You say an x-ray. The use of 'a' or 'an' is determined by the first sound of a word, a vowel sound or a consonant sound. In the case of x-ray, it's said ex-ray so you use the 'an'.

Answer 2

The article 'an' is used; an x-ray.

The indefinite article 'an' is used when the word that follows starts with a vowel sound; the noun x-ray, pronounced 'ex-ray', starts with a vowel sound.

The indefinite article 'a' is used when the word that follows starts with a consonant sound, for example a boy, a girl, a cat, a dog.

The choice of the article used does not depend on the actual first letter of the word, it is dependent on the first sound of the word, for example a hat, an hour.