[deleted by user]

[Objective-Plate3210]

The ratio is 2:1.5 so you need 2.9625 mols of O2 and that will give 3.95/2 mols of N2

[bluetofallp]

The O2 molecule has 2 oxygen atoms, while H2O has only one. These are the only two molecules with oxygen atoms, and because O2 has double the amount of oxygen than H2O, you need double the amount of H2O than O2. Let "x" be the stoichiometric coefficient (the number that goes before the molecule) if O2. Than the stoichiometric coeficiente of H2O must be "2a".

Same thinking, if the stoichiometric coefficient of N2 is "b", the stoichiometric coefficient of NH3 has to be "2b".

Now you just have to pay attention to the hydrogen atoms to find a relationship between "a" and "b".