You may have correctly set the exponents equal to each other and found that $\displaystyle{x}={6}\usepackage{cmbright}\Huge\$ , but then you evaluated the expressions on each side of the resulting equation for $\displaystyle{x}={6}\usepackage{cmbright}\Huge\$ and found $\displaystyle{9}{\left({6}\right)}-{6}={48}\usepackage{cmbright}\Huge\$ and $\displaystyle{6}+{7}{\left({6}\right)}={48}\usepackage{cmbright}\Huge\$ . This is not the value of x.