Hint: Think about a gas which is very stable and won’t make the eatables stale and it is also abundant in nature.
Complete step-by-step answer:
Potato chips bags are filled with Nitrogen ($N_2$) gas.
They are not filled with air because the oxygen in the air reacts with the contents of the chips (oxidation), which leads to the spoilage of the eatables. The eatables become rancid and start smelling.
Nitrogen creates an inert atmosphere which helps to preserve the chips inside.
Inert (Noble) gases are not used because they are expensive and $N_2$ gas is also abundant in nature.
The triple bond in $N_2$ makes it really stable and thereby its reactivity is less, hence it is often considered as inert.
Note: Such problems are inspired from real life examples. Observation of real life scenarios and developing an understanding of them is important. These problems can be solved by considering the behavior of gases.