The operation § associated to any number means “divide the number by 3”.
Is the set of integers paired with the operation § a mathematical system?
§9=3
§3=1
Is §1 ∈ Z?
where Z=set of integers, and ∈ ≡ "is in"
Is the set of integers paired with the operation § a mathematical system?
§3=1
Is §1 ∈ Z?
where Z=set of integers, and ∈ ≡ "is in"