 Now, before we go anywhere, before we do anything with math, you have to learn how to do things manually. As I said before, you've got to stop using the calculator or stop using it as much as you are. Basically, you have to learn how to do things manually. So, I'm just going to show you how to add and subtract and multiply and divide by hand. Now, you don't have to do everything you come across by hand, but it's good to know how to do it because it allows you to understand how numbers work and how you can put them all together. Now, let's talk about adding and subtracting, okay? Let's say I give you two numbers. 12 plus, 25 plus 12. Now, all you do, you line them up. 5 plus 2 is 7, and that's 3. Now, what if you get anything that goes higher than 10? 29 plus 17. Okay. You got 9 plus 7. 6 is 16. So, what you do is you carry the 1 up here, okay? Then you got 1 plus 2 is 3. 3 plus 1 is 4. Easy? Simple. What if you had a huge number? 2, 0, 9, 7, 1 plus 9, 2, 8, 2. Well, 1 plus 2, 3, 7 plus 8, 15. You carry the 1 up here. 9 plus 1 is 10 plus 2 is 12. You carry the 1. 1 plus 9 is 10. 0, you carry the 1, 3. Simple as that, okay? If you want, you add your little column so it becomes easier to read. Now, if you have decimals when you're adding numbers, what you do is you line up the numbers according to their decimals. So, for example, if I give you two numbers, 2.57 and 1 or 12.5. So, what you do is you line up your numbers according to the decimals. So, you go 2.5712. You're adding them based on this boundary. So, there's no number here. So, you just add a 0. So, that becomes 7. 5 plus 5 is 10. So, you add your 0, bring the 1 up here. 1 plus 2 is 3. 3 plus 2 is 5. Okay? Nothing came up and then you have your 1. You keep it down here and the decimal place stays there. Okay? So, 2.75 plus 12.5 is 15.07. That's adding. Now, we're going to deal with subtracting, okay? Come. Okay? So, we talked about adding. Now, we're going to do subtracting. 12 minus 7. Now, what you do here is you're subtracting 7 from 12 and you've got to line up your numbers a bit. Now, 7, you can't take 7 away from 12. So, what you do is you're going to borrow 1 from here. So, you cross this off. This becomes 0. The 2 becomes 12. 7 minus 12 is 5. Now, obviously, that was simple. Okay? You already knew that. But, when you go to higher numbers, that's the same process you're going to be using. Okay? So, if you have 257 minus 29. Okay? So, what you do is you can't take 9 away from 7. So, you're going to borrow 1 from the 5. So, that becomes 4. This becomes 17. 9 minus 17 is 8. 2 minus 4 is 2. And there's nothing to subtract here. So, that becomes 2. That's subtracting. And with the decimals, it works the same way. Line up your decimals and you continue the same way you did with the addition. Okay? So, if you're doing 2.51 minus 1.9. So, the way you do this is there's nothing to subtract here. So, that's just the 0. That just becomes 1. 9 from 5. You can't take, so you borrow 1 from this. This becomes 15. 9 minus 15 is 6. 1 minus 1 is 0. And your 0's line up here, you put it down here. Okay? That's subtracting. Let's go on to multiplication, okay?