 We can take a look at calculating the equivalent resistance in series circuits. So the equation that we have for the equivalent resistance in series circuit is the sum of the individual resistors. And if I've just got two, it's adding up the two, but if I had three, or four, or five, the dot dot dot just means continuing the pattern for as many resistors as you have. So let's do a simple example. One with two resistors. So let's say I've got a 42 ohm resistor and a 21 ohm resistor. I'd add those up and I get 63 ohms. You might have things that are three resistors. So this particular example, I've got a 1.5 ohm resistor, a 2.0 ohm resistor, and a 6 ohm resistor. And with a three, I would just add up all three of those values, giving me 9.5 ohms. And the unit here is ohms, and that's the capital omega symbol. Now one of the other things that you might come across sometimes is a situation where instead of being given the individual resistances and finding the equivalent resistance, maybe you've been given an equivalent resistance value and one of the two, so maybe in this case R2. But you have to find out what the unknown R1 is. Now if I were to just do the algebra on the equation itself, what you would see is that you want to take that known R2 and subtract it from both sides, so you'd have the equivalent resistance minus R2, and that will give you your unknown R1. For this particular example that I've got here, that means you take your 3.2 ohms, subtract it over to the other side, and that would give you your R1, and in this case 5.4 minus 3.2 ohms will give me the 2.2 ohms. Now you can always double check your calculations here because you could take this and put it back into the original form, and I'm just going to do this sort of on the fly here. And if I was going to rearrange this equation, I'd have my 3.2 ohms, and that's going to go back over here but be added on this side, and that should add up to give me the equivalent resistance I know I was supposed to get. So in this case, the unknown resistance would have had to be 2.2 ohms in order for it and the known 3.2 ohms to add up to give you that equivalent resistance. So again, just like any equation, it can be rearranged to solve for an unknown, but in the series circuits, it's really quite straightforward in terms of that the individual resistances just add up to give us our overall equivalent resistance. These are just a few example calculations that I went through kind of quickly, but rewatch it if you need to and ask me questions.