In the balanced equation (picture included) how many moles of o2 molecules and o2 atoms react?

1) The answer is: 2 moles of oxygen molecules.

Balanced chemical reaction of methane combustion:  

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g).

Coefficients with the lowest ratio indicate the relative amounts of substances in a reaction.

In fronf of oxygen molecule is coefficient 2.

2) The answer is: 4 moles of oxygen atoms.

In one molecule of oxygen there are two oxygen atoms, so in two molecules there are four oxygen atoms.

there are two significant figures.