Answer
Partial Pressure of $H_2 = 317 \text{ torr}$
Partial Pressure of $N_2=51.7\text{ torr}$
Total pressure = $368\text{ torr}$
Work Step by Step
Partial Pressure of $H_2$
We must multiply the pressure of $H_2$ by $\frac{2}{3}$ to account for the increase from two liters to three liters.
$475\text{ torr}*\frac{2}{3}=317 \text{ torr}$
Partial Pressure of $N_2$
We must multiply the pressure of $N_2$ by $\frac{1}{3}$ to account for the increase from one liter to three liters.
$0.200\text{ atm}*\frac{760 \text{ torr}}{1 \text{ atm}}*\frac{1}{3}=51.7\text{ torr}$
Total pressure = Partial Pressure of $H_2$ + Partial Pressure of $N_2$ = 317 + 51.7 = $368\text{ torr}$
