ok so how in the world did you figure out the first part?? I am so confused with how you went from the variables a,b,k to the variables c and j?
The second part (b) will those be the equivalence class representatives.
I know that 4,23,65 are not the same equiv. classes, but 5, 50, 75 are the same equiv classes. Right?
Do you know what equivalence relation is?
If you do, then you recognize that as a proof that the relation is an equivalence relation.
By the way, a, b & c are natural numbers. While k & j are of course integers.
Do you really know that?
Name us one other number in the equivalence class determined by 4.
How many equivalence classes do you think there are?