So it appears that this is asking for what the volume (V) of the N2 gas is under those conditions. For this we use the Ideal Gas Law:
PV = nRT, where P = the pressure in atm, V = the volume in liters (L), n = the number of moles of gas, R = the Ideal gas constant, which is 0.0821 (atm•L)/(mol•K), and T = the temperature in Kelvin which is the °C + 273
So to solve for V: V = (nRT)/P
V = [(0.020molN2)×(0.0821atm•L/(mol•K)×290K] ÷ 1.5atm
V = [(0.476•atm•L N2] ÷ 1.5atm
V = 0.317 L N2
If you look at each step, you can see that I included the units, because you can see them cross each other out to give you the final product, volume, which is in liters (L).
I hope that helps you understand these types if problems better!