Write the following intervals in set-builder form: (i) $(-3,0)$ (ii) $[6,12]$

Solution:

(i) $(-3,0)=\{x, x \in \mathrm{R},-3<x<0\}$

(ii) $[6,12]=\{x, x \in \mathrm{R}, 6 \leq x \leq 12\}$