You correctly factored out the GCF. However, when factoring $\displaystyle{{x}}^{{2}}-{2}{x}-{24}\usepackage{cmbright}\Huge\$ , you reversed the positive and negative signs in the binomials. To correctly factor you need to find two numbers whose product is $\displaystyle-{24}\usepackage{cmbright}\Huge\$ and whose sum is $\displaystyle-{2}\usepackage{cmbright}\Huge\$ , not 2.