Let m_1, m_2, ..., m_r \in \mathbb{Z} be pairwise relative prime, let a_1, a_2, ..., a_r \in \mathbb{Z} The system of linear has a unique solution up to M = m_1m_2...m_r

There will be a unique solution up to the multiple of all congruence m.

More About: https://www.uvm.edu/~cvincen1/files/teaching/spring2017-math255/quadraticequation.pdf