First of all, of course, you write down the reaction and equalize it.
I don't know how to write chemistry equations here, so I used my refined Paint skills
In stoichiometry (calculations of quantities in reactions), you should, at least most of the time, work with moles because it's often easier.
In this case (this is only available for GASES at STP!!!), you can use the formula
Again, this is true only for gases at STP.
Putting this in the reaction, we have: (on the upper side you write the coefficients of the substances, and the quantities given in the problem below)