Trying to improve my skill

What does a numerical subscript following an element in a chemical formula mean?

If you try to move a piano and are unable to move it, did you perform any work in the scientific sense of the word? yes? or no? this question is worth 20 points! let it be correct!

An object of mass 10.0 kg and volume 1000 ml and density 10 g/ml sinks in water who’s density is 1.0 g/ml. what is the mass of the water which has been displaced in kilograms