Correct. Using the equation for work, $\displaystyle{r}=\frac{{W}}{{t}}\usepackage{cmbright}\Huge\$ , you find that the rate of the drain is $\displaystyle\frac{{1}}{{x}}\usepackage{cmbright}\Huge\$ (because it empties the tub in x minutes), and the rate of the hose is $\displaystyle\frac{{4}}{{x}}\usepackage{cmbright}\Huge\$ (because it can do 4 times the amount of work in the same amount of time). Since you know that it takes both the drain and the hose 8 minutes to empty the bath, you can write $\displaystyle\frac{{1}}{{x}}+\frac{{4}}{{x}}=\frac{{1}}{{8}}\usepackage{cmbright}\Huge\$ . Solving for x yields 40 minutes.