Proof for $\gcd$ operation, with out using technique of showing counter-example.

Question

Let, denote the $\gcd$ finding operation by $G$. Need proofs for two below statements, with out showing a counter-example case.
1. Proof to show that $G$ does not obey the Cancellation Law. In other words, given three positive integers $a, b$ and $c$, s.t. that $c G a = c G b$, but $a \ne b$.
2. Proof to show that $G$ is not distributive over $+$ operation, i.e. given three positive integers $a, b$ and $c,$ s.t. :
$c G (a + b) \ne (c G a) + (c G b)$