Correct spelling, explanation: eating is the correct form because to create this form suffix -ing is added to a core word. Here the core word is eat. eat and -ing gives eating. There is no need to double t, since it is preceded but two vowels. Therefore eatting is incorrect.

Definition of eating:
verb, gerund form of eat, to consume food
While she was eating lunch the phone rang.
Stop eating and listen to me!

Incorrect spelling, explanation: eatting is a wrong spelling since we don’t double the t in eating. We only double the last consonant with suffixes in the case of consonant-vowel-consonant.

Incorrect spelling

Incorrect spelling

Incorrect spelling