I need to prove that each of the congruence classes listed above are different, and that any other congruence class [a](for any integer a) has to be equal to one of the congruence classes listed.
I know in order to prove the second part I must show that a is a subset of a congruence class and that congruence class is a subset of a to show they're equal but I'm not sure how to go about the first part.