Law of Constant Proportions

Discus whether the carbon dioxide that you breathe out and the carbon dioxide that your friends breathe out are identical. Is the composition of the carbon dioxide of different sources same?

$100 \mathrm{g}$ of mercuric oxide decompose to give $92.6 \mathrm{g}$ of mercury and $7.4 \mathrm{g}$ of oxygen. Let us assume that $10 \mathrm{g}$ of oxygen reacts completely with $125 \mathrm{g}$ of mercury to give mercuric oxide. Do these values agree with the law of constant proportions?