 So, this problem says, how would you prepare 500 milliliters of 0.3500 molar sodium hydroxide solution starting from a concentration of 1.000 molar, okay? So it said starting from, that means the initial volume, right? So that's going to be 1. And it said, well the other one must be the other molarity, right? What you're going to. So that must be 2. And it said, how would you prepare 500 mils, right? So that must mean, that's what you prepare, just 500 mils of it. So that's got to be 2 as well, right? That makes sense. So what are we looking for? The initial volume. I don't know, did it tell you in liters or milliliters or anything? Doesn't say, so we can put it in whatever units we come up with first, okay? So how do we do something like this? Well we have to remember our formula, m1v1 equals m2v2. And we're looking for v1, so let's isolate that variable. So how do I do that? I'll divide both sides by m1, so I get that. So all we do now is plug and check. So m2, 0.3500 molar times volume 2, 500.0 mils divided by 1.0 molar. So 4, 4, 4. So our final answer is going to be the 466, so 0.35 times 500 divided by 1. So cancel, cancel, right? So we get milliliters, so I get 175.0 mils of solutions. This would be the initial volume that I would need of 1 molar to dilute to 500 mils to get the concentration of 3.500 molar, okay? Any questions on that one? So what you really need to do is remember the formula, m1v1 equals m2v2, okay? And which one's the plug and where?