Lesson 12: Solving Variables on Both Sides of the Equation #6

[One Speaker]

[Any necessary descriptions]

Narrator:

We’re going to solve for the variable C, but we can see that our variable is on both sides of the equation. So we need to combine like terms, so we’re going to do that. We are going to start by bringing our C’s to one side, and then getting everything else over on the other. So we are going to start by adding nine C to both sides. Remember, whatever we do to one side, we’ve got to do to the other. And so, over on the left we have seven, we have negative five C plus nine C. Well, nine and negative five is four, so we’ve got plus four C equals negative nine. And we have minus nine C plus nine C which is equal to zero, so that’s gone.

And now we can subtract seven from both sides, because we want to get our other terms on the other side. Okay, so we are left with four C on the left, and we have negative nine minus seven, which is negative sixteen. And then we need to multiply by the multiplicative inverse of four to get rid of our four. And so what we do to one side we do to the other. So over here our fours can cancel and we’re just left with C. And over here we have negative sixteen over one times one over four, which is equal to negative sixteen over four. And that’s the same as negative sixteen divided by four which is just negative four. So we have found that C is equal to negative four.

(1:36)

Now we can plug this back into our original equation anywhere we had a C, and we can find out if both sides are equal to each other. And if indeed both sides are equal to each other than we know we have the right answer.

(1:51)

Okay, so I’m going to start by rewriting our equation which is seven minus five times C, equal to