Answer
$\delta=1$
Work Step by Step
See graph; we can find $|c-a|=|-3/2+7/2|=2$ and $|c-b|=|-3/2+1/2|=1$. We choose $\delta=1$ (smaller of the two values) so that for all $x$, when $0\lt|x-c|\lt\delta$, we have $a\lt x\lt b$ as can be seen from the figure.