 OK. So this problem, like we were talking about, is problem dealing with radioactivity. So this is showing the chemical equation when uranium-238 isotope releases what we call an alpha particle or helium and atom. So this is just like any other chemical equation. So what's on this side has to equal what's on this side. And on the sides, I'm talking about the number of particles here and here, subatomic particles, that additive. So if we look here, what's happening? If we take this and go here, how many are we missing here? How many protons are we missing here? 90, right? Since we're taking 92 and subtracting 2, we're going to have 90 protons. Is everybody OK doing that type of problem? So once we find out the 90 protons, we already know what the identity of the atom, right? Because that's the number of protons. That always tells us what atom we have, right? So let's look up at the periodic table and we can just give the atomic symbol of this or the elemental symbol. What symbol will we write up here? Th. So is everybody cool with doing that? And then here, we're taking 4 away from 238. So we're going to get 234. So thorium 234. So in other words, when uranium 238 emits an alpha particle, we get thorium 230. So I think these are pretty basic. I think you guys can do these on your own. Maybe we'll go over one more.