Hi, i need help with the following question.

Let $\displaystyle a,b\in\mathbb{Z}$and $\displaystyle n\in\mathbb{N}$. Set $\displaystyle d=gcd(a,n)$.If $\displaystyle d\nmid b$ then prove that $\displaystyle ax\equiv b(modn)$has no integer solutions for $\displaystyle x$.