The thing that we're trying to solve for, the missing number, is going to be equal to, is going to be equal to four times six. What's four times six? That's 24. What's the question mark? 21 plus what is equal to 24? We can, of course, you might just, well, it's going to be three, or if you want to, you could say, well, question mark is going to be, question mark is going to be equal to, is going to be equal to 24 minus 21, which is, of course, three. Which, of course, let me just write this down.