Show that all $x$ satisfying $0\lt |x-a|\lt\delta$ is equivalent to the union $(a-\delta,a)\cup (a,a+\delta)$ where $a$ is any real number and $\delta\gt 0$.

Problem: 

Show that all $x$ satisfying $0\lt |x-a|\lt\delta$ is equivalent to the union $(a-\delta,a)\cup (a,a+\delta)$ where $a$ is any real number and $\delta\gt 0$.

Answer: 

It is true that $0\lt |x-a|\lt\delta$ is equivalent to the union $(a-\delta,a)\cup (a,a+\delta)$.