 Okay. Let's try this. Q and E combined to form an ionic compound in this formula is QE. Q and Z combined to form an ionic compound in this formula is Q3Z2. What is the charge for Q, E, and Z? Okay. Because Q is listed first in both of those formulas, it's got to be a cation. And Z and E are both listed last, so they've got to be anion. It's reasonable to assume that Q is at the same oxidation state or has the same charge in both of those formulas. Okay? So, what we can say effectively is that Q has to be positively charged, so it can be either plus 3, 2 plus 1. E has to be negatively charged, so it can be minus 3, minus 2, minus 1 formula units. So we know that Q and E have the same magnitude, the opposite charges, because of course they have to add together and equal zero at the end. If we look at this, if we look at these numbers over here, this might be the easiest way to look at this. If we look at these numbers over here and we look at these numbers here, 3 and 2, there's only one way to get these to cancel out to be zero. Okay? And if we look and we write it apart, we say 3 Q's plus something plus, plus 2 Z's something minus. So if we've got 2 and we multiply it by 2 here, 2 minus, we can't get Q to equal to 4. Okay? If we take 2 minus here, we can't say 3 Q's is 4 plus all together, because that would mean they were each plus 0.75. Okay? So Z can't be 2 minus. So Z can either be, if Z was 1, right? Then we would have 2 of them, 2 of them, and that would equal 2 minus all together. Okay? Again, there's no way we can get Q to be 2 minus, so Z can't be minus 1. Okay, so we're left with saying that Z is going to be minus 3. So Z's minus 3, and we've got 2 of them. 2 times 3 is 6, right? So we have a total of minus 6 there. 3 times what? Equals plus 6. Well, it's going to be 2, right? So we've got a plus 6 now, plus a minus 6. Does that equal 0? Yes, it does. So the charge for Q then has to be plus 2. And then, of course, when we go back to the first formula, we know that Q and E have the same charge, our same magnitude, different charge. So, of course, E then has to be minus.