Incorrect. The boys' individual rates, in cords per hour, are $\displaystyle\frac{{1}}{{10}}\usepackage{cmbright}\Huge\$ , $\displaystyle\frac{{1}}{{12}}\usepackage{cmbright}\Huge\$ , and $\displaystyle\frac{{1}}{{15}}\usepackage{cmbright}\Huge\$ . Together their rate, in cords per hour, is $\displaystyle\frac{{1}}{{10}}+\frac{{1}}{{12}}+\frac{{1}}{{15}}\usepackage{cmbright}\Huge\$ . If it takes them t hours to chop 1 cord, then their collective rate can also be expressed as $\displaystyle\frac{{1}}{{t}}\usepackage{cmbright}\Huge\$ . Set these two ways of expressing the rate equal and solve the equation.