 OK, so this one is number 10 on the practice test. Calculate the number of grams of NACL and 15 milliliters of a 15% weight volume solution. So you're going to have to know the equation for weight volume percent. So that equation, of course, is percent weight volume equals the mass of the volume over the volume solution. We should be able to figure out the mass of the solute with this information. So let's just manipulate this equation in order to get mass of solute on the side by itself. So the first thing you want to do is divide both sides by 100%. It's going to be mass equals divided by numbers. Then we get the volume here is 15 mills. The weight volume percent is going to be 15% grams per mill divided by 100. But we notice mills cancel here, percent cancels here, and we're left with grams. If we multiply those numbers together, 15 times 15 divided by 100, that tells us how many grams that remains, which is 2.25 grams. But of course with sick things, because this says 15 there, we're going to have to take this to 2.3 grams. So notice the molecular weight we never used, even though.