Answer:
Sulphur (iv) Oxide (SO₂)
In a single SO₂ Molecule... There's 2 oxygen atoms.
Now
If there a 6 molecules of SO₂
Quick Math
6 x 2 = 12.
Simply put...
THERE'S 12 OXYGEN ATOMS WHEN THERE'S 6 SULPHUR ATOMS.
Another way to look at it is
In SO₂
The ratio of Sulphur to Oxygen is 1:2
Meaning that the amount of Oxygen is double that of sulphur
Since the question stated "When there are 6 sulphur atoms"
It simply means that there's gonna be 12 Oxygen atoms.