 Okay, so let's go ahead and attempt this example. This is one of those examples where you're comparing an unknown and its physical properties to some known physical properties and the implication is that if the physical properties are the same then they're the same substance. So this is overall a density problem, so the given numbers are there written on the left hand side of the paper. The mass is 35.4 grams, the volume 3.11 centimeters cubed and we're looking for the density. Of course it'll help if you remember the density equation, density equals mass divided by volume. And then you just plug in those variables, the numbers that you have for those variables. So 35.4 grams divided by 3.11 centimeters cubed and when you do that calculation of course you get 11.4 grams per centimeters cubed. And from there you want to look at the table that's presented to you. The densities of some common substances here and just look through that table you find something that's very close to that number, 11.4 grams for your cubic centimeter and I see that lead is in fact 11.4 grams for cubic centimeter. So the answer to that problem is going to be lead, okay? So hopefully that makes sense, if not let me know.