Correct spelling, explanation: easier is the correct form as it is a comparative adjective of easy. According to the rule, y becomes i in a word in which at the end there is a consonant and y. There is s before y in easy, therefore the correct form after adding the suffix is easier. Easyer is incorrect because there is a consonant before y.

Definition of easier:
adjective, comparative of easy; something not as difficult as something else, more comfortable
It would have been easier to understand the subject if you had attended lectures regularly.
It’s easier for Jim than me to wake up early in the morning.

Incorrect spelling, explanation: easyer is a mistake and easier is the correct form because when adding the suffix, y at the end of the word remains only if it is preceded by a vowel. In the case of easy, y is preceded by s, therefore a consonant, so y transforms to i. Thus easier is the correct spelling.

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling