Okay, addition and subtraction with scientific notation. As you'll probably remember, each number that's written in scientific notation has two parts: the coefficient or the mantissa, and 10 raised to an exponent, which we can call the power. When we do addition and subtraction problems with scientific notation, we hope that the powers are the same because it makes the problem much easier. But if they're not the same, it isn't the end of the world. I'll show you how to solve those problems too. Let's look at this addition problem. In this case, the first thing I always want to look at is the powers. And since they're the same (10 to the fifth in both cases), I'm set. Here's all I have to do: I take the coefficients, and since this is addition, I add them together (3.769 + 4.21). These two guys and I do that math. And now, since the powers were the same, all I do is bring this power down (10 to the fifth) and use it in my final answer. Simple as that. So my answer is 7.979 times 10 to the fifth. All I have to do is do the math, and then I just bring down 10 raised to the exponent. Here's a subtraction problem. I'm not even going to go through the whole thing because I think it's so easy. I just look at the powers here. They're the same, so all I have to do is the subtraction (8.14 - 2.01). There's the answer. And then I take 10 to the negative second, I pull it down here, and reuse it in my final answer. I'm done. So you may be asking yourself, what do you do if the powers aren't the same, like this example here? I have 10 to the...