1.6.62 Fields, Groups, Rings

condition: Let \( \mathbb{Z}[x]- \) be an additive group of polynomials with integer coefficients. Consider a subgroup \( H \) of the group \( \mathbb{Z}[x] \) such that all polynomials in it are divisible by \( (x-3) \). Prove that \( \mathbb{Z}[x] / H \cong \mathbb{Z} \).