Proof Writing · Hard problem

Assume $n$ is not divisible by $6$ and $n$ is divisible by $3$, and derive a contradiction.

Assume $n$ is divisible by $6$ and $n$ is not divisible by $3$, and derive a contradiction.

Assume $n$ is divisible by $3$ and show $n$ is divisible by $6$.

Assume $n$ is not divisible by $3$ and show $n$ is divisible by $3$.