What does elements of
$$\displaystyle\frac{\mathbb{Z_n[x]}}{\langle ax+b \rangle }$$ lookes like
Every time i try to solve this kind of question i got stuck here .As we know that elements of $\mathbb{Z_n[x]}$ lookes like
$$a_0+a_1x+a_2x^2+a_3x^3+....+a_mx^m$$where $a_0,a_1,a_2..a_m \in $ $\mathbb{Z_n}[x]$ and the elements of above ring looks like $$a_0+a_1x+a_2x^2+a_3x^3+....+a_mx^m+ \langle ax+b \rangle $$, but what is next .Please help
Thankyou