Correct spelling


Correct spelling, explanation: tries is a base word try and a suffix -es, used to create plural nouns or third-person forms of verbs. In the case of try, similarly to cases of many words ending in y, when a suffix is added, the y often is changed to ie, to make the pronunciation more intuitive and the spelling looks neat.

Definition of tries:
verb, the third person of try
1. to have an attempt at something
He always tries to be positive, even on the gloomiest days.
2. to test something, to see if something works (usually: test out)
Amelia tries out almost every recipe she sees on TV.
noun, plural of try
1. a possibility to have many attempts at something
I’m not athletic, but after many tries, I finally managed to do a cartwheel.

Incorrect spelling


Incorrect spelling, explanation: you might’ve already noticed that in general there are not many English words ending in ys. It might happen when it’s a proper name and an apostrophe (like Denny’s), but when it comes to derivation, the y has to be changed to i. In the case of try and a suffix -es, it becomes tries. Trys would be confusing to pronounce as the consonant cluster is very non-intuitive to a speaker.