I’m very new to chemistry so if you can help me that would be great!

The answer would be 21. I got this answer because the subscript numbers that are to the right of each element are the amounts of atoms. So there is 6 carbon atoms, 12 hydrogen atoms, 2 nitrogen atoms, and 1 oxygen atom in one molecule of the chemical formula you provided me with. But since the question asks us for two of these molecules, just add up the amount of atoms in one molecule and multiply by 2.

That result from subduction of oceanic plates beneath lighter continental plates. most of the earth's volcanoes are located around the pacific ring of fire because that the location of most of the earth's subduction zones.

The correct answer is "atomic weight".