 Okay, so in this problem, we're wondering, what's the mass of zinc hydroxide? We know the mass of zinc oxide and, or zinc 2 oxide, I should say, and zinc 2 hydroxide, and water here. So the mass of water is 6.3 grams, the mass of zinc 2 oxide is 28.4 grams, okay? So if we know the law of conservation of mass, okay, the law of conservation of mass states that everything on one side of the reaction equation has to weigh the same amount as everything on the other side of the reaction equation. So all the reactants must equal, the mass of the reactants must equal to the mass of A, in this case, must equal the mass of B, okay? If not, what's happened? You've either created or destroyed mass, and of course, if you know Dalton's atomic theory, you can't do that, okay? So in this case, all we need to know is that the mass of zinc oxide plus the mass of water should equal the mass of zinc hydroxide, zinc 2 hydroxide. So this is a fairly straightforward problem because it gives you this mass and this mass. If one of these masses wasn't given and it asked you to figure out the mass of zinc hydroxide, you would actually have to do what we did in the last problem, change this to moles, go to moles of zinc hydroxide and then go back to grams of zinc hydroxide. But since we've got both of the masses of the reactants, we don't have to do that. All we've got to do is plug in values to this equation. So we've got 28.4 grams plus 6.3 grams that equals the mass of zinc hydroxide, zinc 2 hydroxide, so the mass of zinc hydroxide is 0.7. So hopefully that number is different than what you were putting on the computer and it'll work out the way.