 Okay, so let's try this one. Calculate the weight-weight percentage of platinum in a gold ring that contains 14 grams of gold and 4.500 grams of platinum. Okay, so this is the one that we gave in class, right? And we were talking about weight-weight how it's best to do weight-weight percentage when you've got a solution of two solids, okay? Because you can get both the solution weight and the solute weight, okay? So the first thing you want to do is figure out which one is the solute, okay? So in a solution, of course, the solute is the one that's found in the least amount, okay? So like a solution contains two or more things, right? In this case, you've got gold and platinum, gold being 14 grams, right? And platinum being 4.5 grams, so platinum is the solute, okay? Because it's in the least amount. So the mass of the solute is going to be 4.500 grams. The mass of the solvent is going to be 14.00 grams, okay? And then that means that the mass of the solution equals the mass of the solvent plus the mass of the solute, right? 4.5 plus 14, so that's 18.5. So now you've got to remember the weight-weight percent calculation equals mass of solute over mass of solution 100 percent. So now all we've got to do is plug these numbers in. So of course this is the mass of the solute, this is the mass of the solution, so these are the two numbers you're going to use. So 4.500 grams divided by 18.50 grams times 100 percent. So the one thing I want to caution you about is if your calculator has a percent button, don't use it, okay? Just think of the percentage sign as another unit, okay? So go 4.5 divided by 18.5 times 100. So here grams will cancel out, right? So we won't have that unit grams anymore. And if I read this correctly, it's a four-sig fix. It's going to be 24.32 percent weight-weight of platinum in this room. So that's a nice, extensive thing for you.