Solving Math Problems With a Variable

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Math problems with variables are identifiable by their use of an unknown, which is usually indicated by an "x," "y" or "z." Find out how to get rid of terms that have nothing to do with "x" with help from a math teacher in this free video series on math help and lessons.

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Video Transcript

So, how do you solve math problems with a variable? Hi, I'm Jimmy Chang. I've been teaching college mathematics for nine years, and solving math problems aren't our favorite thing in the world, especially when it comes with equations with a variable, which means an unknown, otherwise known as x, or a y, or a z. But, here's a brief introduction as to how to do one of those equations with a variable, and after a while you'll see that it's going to be pretty straightforward if your equation just has one variable. Now, here's an illustration. You have two x minus three is equal to seven. Your objective is to solve for x. In other words, find out the missing number that x happens to be. So, because x is the number that you're looking for you want to get rid of any term that has nothing to do with x. Case in point, minus three. The minus three has nothing to do with the two x, so what you want to do is move it to the other side. So, you always want to use the opposite operation, and because you're subtracting by three you want to add three to both sides, but as part of a definition of an equation you want to preserve equality on both sides. In other words, you want to be sure that both sides are equal to each other, so that means that you have to do the same operation to both sides. In other words, if you add three on the left you have to add three on the left as well; otherwise, the equality is not preserved. And then you do the math. Two x still stays two x. Negative three plus three; those cancel out completely, and you're left with seven plus three is equal to ten. Now, the number two is multiplied with the x, so again, to solve for x to get x by itself, again, you do the opposite operation. Opposite of multiplication is division, so that means you would divide both sides by two, again, on both sides to preserve equality, to preserve the balance. Two divided by two; that's going to give you one. That's what you're looking for, so you have x equal to, and ten divided by two is going to be five. So, the missing number that you're looking for is five, so I'm Jimmy Chang, and that's an introduction on solving an equation with a variable.


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