lean_workbook_plus_17370

Let $a_1$ , $a_2$ , $b_1$ , and $b_2$ be integers such that \n\begin{eqnarray*} a_1 \equiv a_2 \pmod{m} \\n b_1 \equiv b_2 \pmod{m} \end{eqnarray*} \nShow that $a_1 + b_1 \equiv a_2 + b_2 \pmod{m}$ .