After correctly multiplying exponents to simplify $\displaystyle{{\left({{x}}^{{2}}\right)}}^{{3}}\usepackage{cmbright}\Huge\$ to $\displaystyle{{x}}^{{6}}\usepackage{cmbright}\Huge\$ , you may have mistakenly multiplied exponents to simplify $\displaystyle{{x}}^{{6}}{{x}}^{{2}}\usepackage{cmbright}\Huge\$ in the denominator. The product rule tells you to add these exponents.