Correct. When $\displaystyle{a}={0}\usepackage{cmbright}\Huge\$ , the equation holds true: $\displaystyle\frac{{{0}+{1}}}{{2}}-\frac{{{0}+{3}}}{{6}}=\frac{{1}}{{2}}-\frac{{3}}{{6}}={0}\usepackage{cmbright}\Huge\$ .