You get $\displaystyle\frac{{1}}{{3}}+{\left(\frac{{2}}{{7}}+\frac{{3}}{{4}}\right)}\usepackage{cmbright}\Huge\$ by using the associative property to regroup. Then you get $\displaystyle\frac{{1}}{{3}}+{\left(\frac{{3}}{{4}}+\frac{{2}}{{7}}\right)}\usepackage{cmbright}\Huge\$ or $\displaystyle{\left(\frac{{2}}{{7}}+\frac{{3}}{{4}}\right)}+\frac{{1}}{{3}}\usepackage{cmbright}\Huge\$ depending on which addition you apply the commutative property to. Neither of these resulted in $\displaystyle\frac{{2}}{{7}}+{\left(\frac{{1}}{{3}}+\frac{{3}}{{4}}\right)}\usepackage{cmbright}\Huge\$ .