What is a fraction of 12?

That completely depends on what "the fraction" is.

Examples:

- - 1/12 of 12 is 1.

- - 1/4 of 12 is 3.

- - 1/2 of 12 is 6.

- - 5/4 of 12 is 15.

etc.

If you want to find equivalent fractions to, say, 3/4, you can multiply the numerator and denominator by the same number. You don't change the value of a fraction if you multiply its top and bottom numbers by the same number because you are just multiplying by 1.