 Okay, so if we have two samples of carbon dioxide that are taken from different sources and they're decomposed into their constituent elements, we find one sample produces 4.8 grams of oxygen and 1.8 grams of carbon and the other sample produces 17.1 grams of oxygen and 6.4 grams of carbon and we're going to show how these results are consistent with the law of constant composition. So I've written down the masses of oxygen and carbon from sample 1 and sample 2 respectively and what we're going to do here is just use that law of constant composition. Remember we do the mass of element A in sample 1 divided by the mass of element B in sample 1 and that should equal, if it divides by the law of constant composition, the mass of A in sample 2 and the 2. So these two numbers should be equivalent. So let's just see if they are okay. So what do we got here? So the mass of oxygen in 1 divided by 0.7. Here's hopefully the masses of the other, the ratio of the masses. We can see 2.7 equals 2.7 so this is the law of constant. So if there are any questions, we'll do another one in a second.