Incorrect. Starting with $\displaystyle{{s}}^{{2}}={50}\usepackage{cmbright}\Huge\$ , simplify the equation into the form $\displaystyle{{s}}^{{2}}=\usepackage{cmbright}\Huge\$ something before solving for s. Remember that $\displaystyle\sqrt{{{{s}}^{{2}}}}={s}\usepackage{cmbright}\Huge\$ since s is positive.