algebra in physics and chemistry

Question

Q1: A water molecule has two hydrogen atoms and one oxygen atom.The atomic weight of water is 18units and that of hydrogen is 1unit .Find the atomicweight of oxygen.

 

=>I think the answer is16 units but I need confirmation 

Answer 1

Yes, you are correct.

 

The 2 hydrogen, weighing 1 unit a piece take up 2 units. Subtracting from the total weight of 18 leaves 16 units for 1 atom of oxygen.