that is, the set of all equivalence classes in , where the representatives are less than and relatively prime to (including 1)
since 5,7, and 11 are the integers between 1 and 12 that are relatively prime to 12.
is an Abelian group with respect to (you know what means, right?).
so what would look like for some prime ?
can you find the order of the elements? do you remember how order is defined?